J. Michael Howard answers questions about quartz in Arkansas
Q. I live in Mt Ida, Arkansas. I am interested in Geology and the differences in quartz crystal formations in shale and sandstone. Are surface pockets of crystal a good indication of what might be found deeper in the ground? I've talked to many crystal miners and their viewpoints are many and varied. Is there any right answer to locating pockets and veins of crystal? Stuart Schmitt, email@example.com
A. Stuart, you have asked a series of complex questions. I will break them down and try to answer each one so all the readers can understand.
Part 1 - the differences in quartz veins and their crystal formation in shale versus sandstone host rock. Shale is composed of tiny particles of clay which have been compacted and squeezed and are bound together to form the rock we call shale. Sandstone is composed of sand grains with some type of cement or binder holding the grains together. This binder is often silica, or iron oxide, or clay. Fractures in shale expose only clay particles to any vein-forming hot water. Fractures in sandstone expose quartz grains and if the sandstone is silica cemented, then broken fresh faces of quartz to the incoming fluids.
This one fact is very important and explains why quartz crystal formation is different in these two rocks. The shale has few easy sites, compared to sandstone, for quartz to nucleate (that is, begin to grow). So in shale, quartz begins to be deposited uniformly over the entire surface. A lot of small milky crystal formation slowly begins, during growth, to produce larger oriented patches of larger milky crystal growth. Then growth is apparently rather rapid until the vein is completely filled. Usually shale-hosted veins have little collectable rock crystal (clear quartz) and usually what they do have is restricted to the middle of the veins.
Of course, in the Ouachita Mountains, these veins may have broken and reformed several times, making the system appear much more complex. Shale has another property due to its behavior when faulted or broken. It tends to smear along the break and seal itself off, effectively reducing the opportunity for silica-rich fluids to deposit quartz. Sandstones in the Ouachita Mountains were brittle and broke and fractured into many fragments during the mountain-building processes. When hot silica-rich waters reached the fractured sandstone beds, they had lots of channelways to move through. On the walls of these channelways were broken sand grains, often oriented properly to allow relatively rapid initial growth of crystal.
Rapid growth is often recognized by the presence of milky quartz. Some sand grains which were not oriented properly quickly dissolved and the available silica was redeposited on the growing crystal, along with silica which came into the vein with the hot water. When you look at a typical quartz cluster from Arkansas on sandstone matrix, the crystal is milky at the base where the crystal is attached to the matrix and clear at the tip. Now you know why. Rapid growth captures a lot of fluid and leaves behind many tiny holes which are filled with this fluid. Light refracts off this fluid and the sides of the tiny holes and the crystal appears milky.
Part 2 - Are surface pockets an indication of what might be deeper in the ground? Most definitely! However, there are a few restrictions I will place on this answer. If you have pockets on the surface and the host rock does not change character, then your chances are good that crystal-bearing pockets extend to some depth. If the host rock was a sandstone at the surface and changed to a thick bed of shale, you are probably going to be out of luck on finding good veins in the shale. If the host rock is alternating thicker beds of sandstone and thin beds of shale and you find crystal pockets in the sandstone, you probably will have some crystal at depth.
Many local factors also enter into the situation. How close the site is to a major fault is important. Large low angle faults, geologists call thrust faults, may have shoved a large area of predominantly sandstone rock over underlying shale. The sandstone above the fault plane may be highly broken up and perfect for quartz deposition. But if the fluids never reached it for some reason, then even the properly "prepared" sandstone host will not have significant mineralization.
Before World War II, most of the local diggers in the Ouachita Mountains were convinced that if you were digging on a crystal bearing zone and the crystal veins became solid and milky at the bottom of where you were digging you would never get to any good clear crystal by digging any deeper. But the drilling and testing by the Federal Government during WW II proved them all wrong. Drilling showed clear, well-formed, crystal at 200 to 500 feet in depth at some of the abandoned locations. The Blocker Lead #4 site is an excellent example. This is now called the Ron Coleman mine and is near Blue Springs in Garland County.
You comment that the miner's opinions are many and varied concerning quartz bears discussion. Each miner's opinion is based on his/her own background, experience, and educational level. Even a college-educated person can have some unusual ideas if they are thinking about something which they have no formal education concerning. This is not to say that much of what the miners say is not based on something they have seen or experienced, but simply that a mineralogist or geologist, due to their formal training concerning things geological, might make the same observation as the miner and reach a totally different set of conclusions.
I am certain that if you tell some of the miners what I have stated here at least one of them will totally disagree with my thoughts and conclusions concerning quartz growth and formation. But he should be prepared to state, based on his own observations, what he thinks about crystal formation so that I might analyze his conclusions, too! If he can't or won't do that, then I can't take his comments seriously. The purpose of any discussion is not to show someone is right and the rest are wrong, but to come to an understanding of what people think, how they drew their conclusions, and which of those conclusions stand up best to critical analysis, thought and testing, so all can learn.
Part 3 - Is there any right answer to locating pockets and veins of quartz crystal? Well, there are several things to do to make yourself more knowledgeable concerning how to find quartz veins with good clear crystal.
First, talk with all the people you can who are in the business. They have a lot of first-hand knowledge based on their experience that a novice miner needs to know. Many of the folks are down right friendly and will help you all they can. They might even let you assist them in mining some quartz so that you gain experience. Don't be bashful. Everyone starts to learn sometime. We are all on the same path. Some are just starting and others have been traveling on this journey for a while.
Second, you need to know something about general geology and the geology of the crystal-bearing areas. I think Garland County Community College in Hot Springs has a summer general geology course. Also, UALR has a summer course by one of the Earth Science Department instructors entitled "Geology of Arkansas". Take the GCCC course this summer and the Geology of Arkansas course next summer. Have some patience. It takes some time to learn and begin to understand how to apply what you have learned to what you want to do, which is to find some good quartz crystal.
I also suggest that, when you have time, you visit the library of the Arkansas Geological Commission in Little Rock. Tell the librarian that you wish to look at a copy of A. E. J. Engel's US Geological Survey Bulletin 973-E, Quartz Crystal Deposits of Western Arkansas. Also, pick up a free quartz pamphlet and a free copy of an article by Howard and Stone titled Quartz Crystal Deposits of Arkansas and Oklahoma.
Good luck in your continuing education concerning this fascinating topic!
Q.Thank you for your comments concerning my answer to your previous question. Would you recommend following the veins deeper and what might we find?
A. Considering your statements about the unpredictability of where you find pockets, I would simply say that no two quartz veins are exactly alike. About the above question, yes I would dig deeper, at least until I reached the limits of whatever equipment I was working with.
One thing about digging crystal, you are not going to find anymore without further digging. This might be quite evident to you, but for my other readers, I must mention that during a mining operation and shortly after it ends is when the best specimens are recovered, simply because new excavations reveal areas that have not been reachable by surface collecting.
The average person working hard in one spot under good conditions can dig a hole 4'X4'X4' deep in mineralized ground with hand tools in a day. But a backhoe or trackhoe can dig that same hole in the same ground usually in less than 5 minutes! So power equipment is a must to locate any crystal pockets, then to keep the crystal from being damaged it is best dug by hand, if possible. As you well know, someone who doesn't know what they are doing with a trackhoe can damage a good pocket in seconds.
Q. My girlfriend and I have just recently started collecting some of the wonderful quartz crystals in the Hot Springs area, digging a little and buying some. We would like a little general information on the formation of clear quartz, how long it took for the crystals to form, temperatures, how long ago, some info on all the different shapes and names,Thank you very much, Park and Lisa
A. The age -- There is no isotopic method for directly dating the vein quartz, but several indirect approaches have been made. First, the veins are obviously younger than the rocks that contain them. In the Ouachita Mountains, the youngest sedimentary rocks present are Pennsylvanian in age. And quartz veins are present in all sedimentary units, but best developed in two Ordovician sandstones, the Blakely and the Crystal Mountain. Major veins are also present in some of the shale units, such as the Stanley (Mississippian). At one locality many years ago, adularia was discovered with the quartz. Adularia is a hydrothermal feldspar and can be dated. When dated, the adularia gave an age of Triassic, which is a little younger than what most geologists feel is a reasonable age for the quartz.
The most reasonable age appears to be late Pennsylvanian, some 286 million years ago for the last major deposition of the quartz. The veins formed in fractures in the uplifted Ouachita Mountains and late Pennsylvanian appears to be the last of that mountain building process. Some of the quartz is older and many veins show several periods of movement and rehealing. There are several igneous bodies in central Arkansas, and in the contact sedimentary rocks, we find alteration zones with smoky quartz. This quartz dates from about 100 million years ago (middle Cretaceous), the same age as the igneous rocks (they have been isotopically dated with some precision). No one can say how long the period of rock crystal quartz deposition lasted, but the cutoff date on the bulk of the crystal is Late Pennsylvanian. When it started, no one knows, but some vein formation could have begun by as early as late Ordovician.
No one knows how long it takes for a natural crystal to grow! It is dependent on how close the chemical and physical conditions approach those that would be ideal. Factors include composition of the silica-bearing fluids, temperature, pressure, Eh-Ph conditions, nucleation sites, and so forth. I can tell you that a small crystal has usually taken less time to form than a large one in the same pocket, but from pocket to pocket and from site to site, we just don't have the information to know. In the laboratory, under "ideal conditions", synthetic quartz crystals up to 1 pound or greater in weight are usually grown in about two weeks.
As to why some crystal is clear and some is not: Clear quartz crystal had a good life! No major breakage from earth movement and no stress or problems when it was growing. Very much Arkansas crystal has a milky matrix or base. The milky portion contains numerous fluid-filled cavities which scatter the light and present a whitish color. Many times "feathers" or planar flaws may be present. They represent breakage and rehealing of the crystal by additional silica deposition.
Sometimes you may even find a faulted (offset) and rehealed crystal. Many curved crystals are due to multiple breakage and rehealing events. Note I said curved. There is a type of quartz crystal that displays a twisting of the point, but I have never see one from Arkansas. Various colors of quartz are due to either elements like iron or manganese dispersed in the crystal chemically or due to natural irradiation of the crystal in the ground. Some mines have very clear crystal, tip to base, but these sites are the exception, not the rule. Normally, there has been enough structural adjustment of the ground (movement) during or immediately after crystal formation to create milky flaws in the quartz. When the vein is milky, then most of the crystal will have milky bases.
The temperature: This has been relatively well documented. The highest temperatures encountered are around 260 degrees C. Water boils at 100 degrees C unless confined. So the temperatures indicate a considerable depth of burial. You must have that for the water to reach such temperatures.
The mountains we see today are the products of millions of years of erosion. Many miners make a big deal about the fact that most veins are found on ridges or the sides of ridges. Well, it stands to reason. The most resistant layers of rock, sandstone, form the ridges. They were also, if fractured and broken up, the best sites for hot water to move through. Remember, the entire area we now see could have been under as much as 5 miles of rock! So the present day mountain forms have really nothing to do with the formation of quartz some 286 million years ago. With some experience of looking at quartz from various mines, you will find a difference in appearance from one mine to the next. Typical size, luster, clarity, length to width, matrix rock, et cetera that will aid you later if you see a piece, but the site is not given.
You could also get a copy of Collecting Crystals, the Guide to Quartz in Arkansas, which has more information about quartz.
Good luck and good diggin' Mike H.
Q. I was wondering what minerals and/or impurities cause quartz to become "phantomed"? I have found only one "phantomed" crystal--from Ron Coleman's Mine in Jessieville. This particular crystal's inclusions seem to appear gray. (I hope inclusion is the correct word to use here)
I have heard of other "phantoms" from the Mt. Ida area that have blue and/or green inclusions?! Do you know about these? Are there other interesting forms of quartz to be had from this general area? What about quartz scepters?
A. Phantoms are caused by a number of things that might happen while a crystal is growing. Any type of change, such as the chemistry of the water, growth interruption, or earth movement (structural adjustment) would have some effect on nearby quartz veins and the crystals forming in them. Sometimes just the type of host rock determines what type of inclusions may be present.
Now I should define the two terms I used, phantom and inclusion. A phantom is the form of the crystal expressed inside the present crystal faces. It may be due to fine-grained mineral matter that was deposited on the earlier and smaller crystal, or a fine coating of bubbles as the pocket periodically dried out, or as ground up rock dust created by nearby faulting that floated into the pocket and was deposited. An inclusion is simply any material encapsulated or enclosed by the mineral, in this case quartz, as the crystal grew. In gypsum, this may be sand or iron oxide.
In Arkansas quartz, inclusions can be many other minerals. Quartz has had a relatively lengthy time of growth, though episodic, when compared to other minerals. The following minerals and rock materials are often seen included in Arkansas quartz: adularia, thuringite (a variety of chlorite), cookeite, ankerite, calcite, pyrite-marcasite, quartz (as both sandstone grains and small crystals), brookite. Other minerals have been noted as inclusions, but are somewhat rarer in occurrence: cinnabar, stibnite, jamesonite, and galena.
Phantoms take on several forms. Perhaps the most attractive are those crystals containing essentially complete caps or terminations coated with some material to make the point display well. Often these type consist of a fine coating of light-colored almost transparent mineral or tiny bubbles which formed on the point and were coated by the later deposition of clear quartz. Most often phantoms display only two or perhaps three of the prism or side faces of the crystal with a mineral or rock material coating them. Clouds of inclusions sometimes fill the early-formed crystal, which was then coated with colorless quartz.
One mine in Saline County was named the White Cloud mine due to the white cloudy phantoms that were often recovered from it. The materials most often composing the phantoms are: chlorite, bubbles, and tiny shale particles. All of the so-called blue phantoms, black phantoms, "manganese" phantoms and "manganese" inclusions and "carbon" phantoms are actually finely divided particles of black shale, a relatively common host rock in the Ouachita Mountains. I don't care what the crystal dealer or miner says, I have had many of these analyzed and the crystals are always aluminum-rich with no trace of manganese or carbon present. Even some earlier geologists were fouled up on this problem by making guesses instead of having the chemistry run on the material.
I should also say something about chlorite. Little work has been done on included chlorite in Arkansas crystal, but wherever chlorite is present, the host rock is shale-rich. The iron, silica, and other elements necessary to form chlorite in the quartz veins are evidently derived from leaching of the nearby shaley units.
Quartz scepters are rare in the deposits of the Ouachita Mountains. So are Japanese twinned quartz specimens. However, in the past few years, a notable number of Japanese twins have come from the Collier Creek mine and Fisher Mountain, both localities in Montgomery County, and even a few from the Old Coleman mine in Garland County.
Q. Why do quartz crystals have six sides? I found a quartz crystal with four sides, what does this mean? I also found a copperhead snake with 2 heads. Whats up with that? Thanks for answering my questions. When I grow up I want to be a geologist just like you. Your friend, Billy
A. Dear Billy, The structure and arrangement of the molecules that compose quartz (silicon and oxygen) combine in an orderly manner. This arrangement allows quartz crystal which forms in an open space to form as 6-sided crystals. Sometimes quartz may form either as misshapened crystals or be broken during formation and continue to form. Either way, the quartz may show some unusual forms, apparently 4 or even 3 sided, but believe me, with experience, you will be able to tell that something like this has happened.
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Q. I've been reading Miser and Engels, both think that the heat associated with quartz crystal formation in the Ouachitas came from magmas. What is the current thinking on this? It would seem to me that the heat from orogeny might be enough and would explain the very large area of deposits. I am not denying that magma might play a factor in some areas, especially Little Rock. Kenneth Quinn.
Over the years I have thought much about this entire situation, and I am going to tell you that I do not believe any magmatic source was directly related. There are several geologic lines of evidence to support my conclusion and I will present some of them right now:
1) The age dates on the quartz mineralization are all wrong for any known magmatic event in Arkansas. We have magmatic basement rocks that are Pre-Cambrian to Cambrian. We have some Triassic diabasic rocks in extreme southwestern Arkansas and we have many Cretaceous intrusions that range in age from around 108 to 87 million years in age. The dates on the bulk of the quartz veins fall in around Late Pennsylvanian to Early Permian. So none of the known magmatic rocks fit time-wise.
2) The chemistry of most of the igneous rocks is wrong. Here we see a predominantly Cretaceous sub-silicic igneous suite obviously derived from mantle olivine basalts and even mid-mantle lamproites (ultrapotassic rocks), not a granite in the batch. Not even a granodiorite or diorite. It seems too difficult to me to mobilize so much silica from a silica-poor host rock.
3) Granites are known to have quartz veins associated with them -- I'll give you that. Look at those in California and Colorado, and even Nevada. And they have something else associated with quartz veins originating from granite, native gold. We have had over a 100 years of quartz mining in this state and no one has yet to show us a quartz specimen with native gold that came from Arkansas, although I did examinine a faked specimen one time (but that's another story altogether).
So I feel confident that granite is out as a potential source, but where does that leave us in our search for the source of the silica-rich hot solutions? Well, I have thought about that, too. I believe the strongest evidence points toward formational brines and fluids forced out during the Ouachita orogeny (mountain-building process) which took place some 286 million years ago. This is in the correct time frame for the known age of the bulk of the quartz mineralization. Just a few miles west of Arkansas, in McCurtain County, OK, there was a well drilled that went to over 10,000 feet in depth. Below 2,000 feet, the units were described as greenschist facies. We do not see this exposed on the surface in Arkansas, but I feel that it may be there in the subsurface. Kern Jackson from Fayetteville reported years ago on very low grade metamorphic effects (zeolite facies) of some of the surface units.
What is the most mobile phase during any regional metamorphic event? Water, good old H2O. And other very mobile phases at even low grades of metamorphism include silica, mercury, antimony, lead, zinc, and other base metals. This, I feel, is the origin of the hot silica-rich salty fluids that moved up the pressure gradient to the near-surface units where it dumped its chemicals as mineral deposits. The base metal deposits of the Ouachita Mountains of Arkansas always have quartz veining associated with them. We have a minor anomaly around Magnet Cove and Potash Sulphur Springs bodies, but these mineral deposits are unusual, being vanadium- and titanium-rich, obviously sourced from the intrusions and not concentrated from surrounding country rock.
So to answer your question directly, I think the solutions that the quartz veins in the Ouachita Mountains formed from are attributable to metamorphic or deformational pressure sweatout, not any magmatic process.
PS: Good question, got anymore?!?
Q. Mr. Howard, you come highly recommended. Could you please tell me the difference between lascas quartz and quartz? And does a simple test exist to check for lascas quartz. I would really appreciate any help in this area, and any information on lascas.
Brian Wodetzki, Plant Manager, Kemwater North America
A. Dear Brian,
Lascas is the industrial term for a product made from milky vein quartz. The lascas is produced from hydrothermal vein deposits that developed in the Ouachita Mountains at the end of the Ouachita orogeny (mountain building process) at the end of Paleozoic time, some 286 million years ago. It consists of cleaned (of clay and iron and manganese staining) milky to clear quartz that has been graded for chemical purity.
The milky vein quartz along with any rock crystal is first mined, and crushed to about 1.25 to 1.5 inch size, and washed over screens to remove the bulk clay and fines. Then it is heated in an oxalic acid bath to remove any iron or manganese staining and, after cooling, is rinsed to remove the acid. It is then dried and graded.
Grading is done visually over special light tables, where lower grade quartz with matrix attached and off color quartz is removed by hand. It is separated into 4 grades, the highest purity being water clear, then transparent milky, then two lower grades of milky. The only difference between lascas and any ungraded piece of quartz is that the lascas consistently has very low alkali and aluminum content.
Lascas is what is used as the chemical feedstock in the industrial process of growing synthetic quartz. It must meet the specifications of the user, or it will not grow the proper product. If you had a deposit of quartz which you think might have lascas applications, you must have the quartz tested for chemical purity. These chemical analyses are not a simple process and must be conducted by a qualified analytical laboratory, preferably one with a good reputation for their work nationwide.
A number of years ago, we collected quartz from many different sites in the Ouachita Mountains and had the material analyzed by the U. S. Bureau of Standards. They chose the quartz from the Old Coleman pit, near Jessieville, AR, as the National Standard to which all other quartz is compared. There were several deposits that graded nearly as good for lascas quality as the Coleman pit. Lascas is presently produced in Arkansas, not from that site, but from a vein deposit in Saline County by one company.
If I can be of further assistance to you, don't hesitate to ask. Mike H.
Q. Has any Amethyst ever been found in Arkansas? If not, why not or do you think the possibility might exist?
A. Yes, amethyst has been reported in two distinctive geological occurrences. At the Crater of Diamonds State Park in Pike County near Murfreesboro there are sparse amethyst veins that crosscut the diamond-bearing intrusion. Rarely are any pieces of quality recovered by collectors or tourists. When the Park personnel deep plow the diamond field with a bull dozer with a stinger on the back, there is always a chance they will bring some of this amethyst to the surface.
The amethyst from this location looks much like Brazilian amethyst in its crystal size and color. It formed in pockets in calcite veins so it may have either calcite or the impressions of the calcite crystals on the opposite side of the points or crystal terminations. The second location is in Saline County were drusy amethystine quartz veins cut across an altered talc-serpentine body. The crystals from this location are always small, stubby and form pale amethystine crusts on the serpentine host rock. At both locations small dark brown needles of goethite are often encapsulated in the amethyst.
Q. I am going to Mt. Ida and Hot Springs looking for Facet grade quartz. Where is the best place to go? Also is there any place to fined amethyst, of facet grade?
A. No place that I know of for facet grade amethyst in Arkansas. See above about amethyst in Arkansas. As to facet grade quartz, every dealer that handles quartz will have some. It really depends on what size facet rough you need.
Q. Does all the irradiated Arkansas quartz come out that "black" color, or does some of it turn out light? I have a light colored cluster that I was told was natural, but I have also been told clusters are rare. My son's special interest is smoky quartz but we are still learning (the more I learn about quartz, the less I know). Since we did not pay a whole lot for this specimen we are really wondering.
A. It can be difficult to know for certain about the irradiated Arkansas black quartz. If the dealer you purchased the specimen from was honest with you, they would have told you up front that the piece was irradiated. But, barring that, there are a few tips you can look for on your specimen. Does it have good zoned phantoms? Few of the the irradiated specimens have phantoms. If it is light colored, does it have a peculiar yellow smoky color? Irradiated quartz that has set in the sun for several months to a year may fade to have this color.
Natural smoky tends to be smoky to the base, whereas irradiated tends to have a white crystal base next to the matrix rock. If so black you can not see through it and having good surface luster, then it is probably irradiated. The problem is that the naturally smoky crystal is also a product of irradiation, but in the ground by natural processes, not by man artificially.
Many years ago there was one major find of natural smoky quartz on the north shore of Lake Ouachita in Garland County. It had a good surface luster, multiple phantoms, and was a pleasing transparent smoke color. It also had pleasing elongated crystal habit. Just 3 to 4 years ago a find was made, also in Garland County at the Smoky Crystal Mine, of a single vein of gemmy smoky quartz. It also had good surface luster and a pleasing transparent smoke color, but the crystals did not display phantoms and were short and stubby in habit.
For years, around Magnet Cove in Hot Spring County, collectors have picked up natural smoky quartz associated with brookite, a titanium mineral. The smoky quartz from this area often forms elongate crystals, but rarely has good shiny luster. The crystals were etched after they formed so they usually have dull luster. Also, they tend to have very stairstepped sides. Most often they have a peculiar gray color instead of a dark black. Specimens from Magnet Cove are often sold or traded without much cleaning being done to them because most collectors do not know how to remove all the iron and clay matrix stains. But I do, so sometimes I can pick up some real bargains!!
Q. Are there any good books on quartz that aren't totally metaphysical? Or does most info have to be sorted out of more general books?
A. Yes, there are several books concerning quartz family minerals that are worth reading. We wrote a book for this exact reason! Collecting Crystals, the Guide to Quartz in Arkansas (updated 2011) is for beginners to advanced collectors. Other than that, probably my favorite for general information about all types of quartz is titled Quartz Family Minerals by Dake (or Drake), Feener, and Wilson (?) and was published in 1936 (?). It is a small book, but packed with information. There was one US Geological Survey Bulletin, Engel, A. E. J., 1951, Quartz crystal deposits of western Arkansas: U. S. Geological Survey Bulletin 973-E, p. 173-260 that is loaded with information about the veins and deposits of Arkansas.
It contains a lot of information about the general geology of the crystal-bearing region, too. You need to look at used book stores and geology book dealers to get either of these now because they have been out of print for so long. Try Amazon.com or Ed Rogers Geoscience Literature or Geoscience books on the Internet! Search under Geology books or mineral books to find the major dealers.
Q. (1)I have found what I call "smoky" crystal points intermixed with clear crystal in several pockets at my mine (Sweet Surrender Crystal Mine). The mine is in a shale formation. The smoky points have a light golden cast and some have phantoms inside. What causes the smoky color and why would they randomly occur with the clear crystal? With appreciation, Stu Schmitt
A. I have not, unfortunately for me, visited this mine. However, the smoky color of smoky quartz is caused by natural radioactive materials having been present as some time during or after the formation of the crystal.
All crystals, quartz and otherwise are zoned internally, because the fluids they formed from changed during the crystallization process. Aluminum must be present in quartz in trace amounts for radiation to cause the smoky color. The aluminum is present as a rare substitute for silicon in the mineral's atomic structure. So if you have a crystal forming from hot water and the amount of silica and aluminum present in the water varies during the formation of the mineral, then radiation occurs, the crystal will contain smoky phantoms.
Be certain that the crystal is truly smoky and does not just contain gray or black phantoms, because that is an entirely different situation. Inclusions are often deposited on the surfaces of the crystals as they form so you see the shape of the earlier formed crystal inside mother nature's final creation.
A. Trudy in OK, I think the best time is in the spring or the fall when the weather is more cooperative -- cooler and less humid than summer, and less varmints around (like snakes, chiggers, and ticks). Late fall after the leaves are turning or off the trees or early spring before the leaves are real large on the vegetation makes it easier to see where you are going.
A. There are 3 non-destructive tests I know of, but two require some special equipment.
1) Specific gravity: the specific gravity of quartz (rock crystal) is 2.65. This is a measurement of the density of the mineral in relation to the density of the same volume of water. You can easily weight the sphere dry, but you need a special type of scale to get its wet weight. You must suspend the sphere by a fine thread in a container of water and weigh the sphere. Once you have the dry and submerged weight, then you put the values into the following formula:
Specific gravity = weight in air / (weight in air minus weight in water)
Quartz is 2.65 times denser than an equal volume of water. Plastic is less. So are most glasses, except for lead crystal which may be greater.
2) Quartz is optically uniaxial, so if you place the sphere between two crossed polarizer plates and rotate the sphere you may be able to find a uniaxial optic axis figure. It looks like a large fuzzy cross and due to the thickness of the sphere would have multiple color bands coming out from the cross' center. Two lenses from an old pair of polarized sunglasses can be used to check this property. Be certain you rotate one of the two lenses until the field goes black or dark when you look through both before inserting the sphere between them.
3) Spend some time looking into the sphere with both the naked eye and a good hand magnifier (10X preferably). If with the naked eye you see fluid swirl marks, the sphere is glass or plastic. Quartz has not formed from a melt so it would never show swirl marks. Under magnification, look for small spherical bubbles. If present, the sphere is not a natural material. Except for lava flows, nature almost never produces perfect spherical holes, especially not in rock crystal. I have seen these bubbles in both glass and plastic spheres.
4) Look at the internal flaws. Are milky zones or cloudy patches present? If so, it could be quartz. Check these with the hand lens (above) to make certain these zones do not contain small round bubbles. Glass, plastic, and quartz all fracture with a conchoidal or shell-like break. I do not recall fracturing being very common in plastic or glass spheres, but it is a relatively common flaw in quartz spheres. Often you may get a rainbow light reflection off quartz fractures, but if present in glass or plastic, I would expect the same effect.
These are the principal non-destructive tests I know of.
You could always check the sphere's hardness with the sharp point of another quartz crystal, but the seller might get upset if you scratched his/her glass or plastic sphere. Quartz will only scratch quartz with considerable difficulty since they are the same hardness. Be certain to check with the owner before attempting this!
Q. On a recent trip to Arkansas, I stopped at Miller Mt. to collect for a few days, Upon returning home and cleaning them up, I found several gwindeles ranging from 1 1/2" to 6" long and the size of my hand. My question is " Is this crystal formation common in Arkansas? I had thought they were more Alpine in origin. Thanks John Huck
A. I would be very surprised if you truly have gwindels from any site in Arkansas. You are correct about this form being more typically from Alpine-type veins. I have been collecting Arkansas quartz for 35 years and have many specimens from Miller Mountain in my collection. However I have never seen a gwindel from Arkansas. Perhaps you have found some fractured and rehealed crystals which generally may exhibit a twisted habit. If the crystals have a cloudy zone internally and are twisted or bent, then they are not gwindels, but instead are due to repeated fracturing and rehealing of those fractures.
I would certainly like to examine a few of your specimens to see what you are talking about. Perhaps you could mail me a couple to look at and then I could send them back to you. Email me and I'll send you my snail mail address.
Q. I've collected quartz crystals from the Mt. Ida area for many years....I'm curious to know more about the triangle formations on some faces of a very few crystals...my brother who has collected in this same place for many years also says they are called "communicators"......what can you tell me about these triangles ?
A. Dan, the triangular faces which you describe are on the termination faces (those that make the point or terminal end) of the quartz crystals. Quartz crystals typically grow by adding layers of silica onto the terminations. Raised triangular shapes reflect the general shape of the individual face and represent where the last crystal was added. Not enough silica was present to fill the face completely out to make a new flat surface. Triangular pits often represent solution features where silica for some reason was being dissolved from the terminal face. Rarely, triangular pits may represent holes left by very rapid face growth. In this instance, a tiny "stringer" or needle like hole may extend down from the face into the clear crystal underneath. Mystic folks like to call crystals with these features "recorders" and they are (in a scientific sense) in that they record the chemical history of the solutions that were in the pocket as the crystal was growing or dissolving.
also....I have many blue phantoms and I know the color is caused by another mineral in there
Essentially all the specimens with black and "blue" (really gray) inclusions that I have had examined chemically turn out to contain shale, a rock rich in aluminum. Shale is not uncommon as a host rock and with all the movement that took place (geologist's call this movement structural readjustment) while the veins were forming, it is reasonable to assume that at times particles of shale were being washed through the veins by fluid movement. Anything that could wash into the veins during crystal growth could and often was captured in crystals.
...what mineral can cause an inclusion to be blood red in a quartz crystal?
Very few minerals could give a blood red color to an inclusion. Either iron oxide, which is rather scarce, or cinnabar (mercury sulfide) come to mind. In the mercury district in Pike County, during mining some small double terminated crystals that looked like Herkimer diamonds were recovered that contained tiny spots of cinnabar and wires of stibnite or jamesonite. None of these have been reported from the major crystal deposits of the Ouachita Mountains, however. I think I would really need to see a couple of these crystals with the red inclusions to know for certain.
A. Morphologically speaking, both brazil twins and dauphine twins from Arkansas as recognizable twins appear to be extremely rare. However, etchings of crystals from Arkansas indicates that they are very common. During World War II, most of the eye-clear quartz that was submitted for optical and electrical testing was twinned and failed to be usable. I think only about 2 % was untwinned. The problem is that although it might look like a single untwinned crystal, it usually is not! Some specimens show a feature on the prism faces that look like zones or patches of slightly different reflection or luster. These patches are bounded by curved to zigzaggy lines. This is an indication that the "crystal" is twinned.
A. Dear Lisa, The days of "staking a claim" for quartz are gone. The procedure is now by the practice of contract, just like for the commodities of sand and gravel, field stone, or crushed stone. This entire procedure changed about 10 years ago. Nowadays, if you locate a potentially minable deposit of quartz crystal on National Forest land, you must put the property up for sealed bid to the District Forest Ranger. The Ranger will visit the site and evaluate it for a number of factors, including actual size, potential environmental impact, potential visible impact, and so forth. The Ranger determines the actual area to be bid on, along with any restrictions that may be attached to the contract. Then, the property is listed on a sealed bid form and mailed out to several hundred people, who have requested that their name be kept on the mailout list. Any or all of these people have the right to visit the property and bid on it. To win the contract, you must be the highest bidder, not just the locator. This new system has taken all the incentive out of it for individuals to search for new deposits, since just anyone on the list may have a chance to bid.
If you wish to know more about these procedures and how to get on the list, I suggest contacting the Ouachita National Forest, P. O. Box 1270, Hot Springs, AR 71902.
As far as quartz deposits on other than National Forest lands: some deposits may be located on BLM or Corps of Engineers governed lands, both of which are under their own sets of rules and regulations. Also, with privately owned lands, it's between you and the land owner as to what you work out financially. The government is not involved.
As you probably have realized by now, the most important thing in the entire process is to know who or what government agency controls the land you find the quartz on because that will determine what procedures you must go through to obtain the rights to dig quartz commercially.
A. Hi Cassandra, quartz can exist, form and reform in all of these environments because quartz is a stable form of SiO2 (silica) over a broad range of temperatures and pressures. Let's consider the mineral quartz and the rock cycle. If you need to, get an earth science text book and find the rock cycle diagram in it. Now, quartz forms as a mineral in certain igneous rocks, especially those high in silica, say greater than 55% as given in a chemical analysis. Granites are up in the 65 to 70 % silica range. Anyway, you have quartz in a granite. Let's follow it through the rock cycle. Weathering of granite changes the other dominant mineral of a granite, feldspar, into clay and frees the quartz grains to be transported some distance by wind, water, or ice. Once deposited as a sediment, the rock-forming process, termed lithification, compacts and cements the sediment together to become a sedimentary rock. Quartz is relatively hard and chemically resistant usually, so it becomes particles in a sedimentary rock. Let's consider a shale as our sedimentary rock. Shale is often composed of a lot of clay-sized material, usually clay minerals (derived from the weathering of igneous rocks) and some very fine-grained silica as silt-sized particles. Now the quartz that is present here did not form as a mineral in this situation. It was simply transported into this dilemma! Now we begin to bury the rock by additional material being deposited on top of it. Heat and pressure begin to work on the rock. The minerals composing shale will begin to change. First the clay particles will become interlocked as the shale alters to slate, then some will begin to be dissolved and reorganized into mica as more heat and pressure is applied. If the process stops here, the quartz has not changed, but the resultant rock in a phyllite. Continuing with greater heat and pressure, the minerals of phyllite change. The fine-grained mica becomes coarser grained and some of the quartz is dissolved and regrown on to quartz grains that are better oriented for growth to occur. The resultant rock is a schist. Then with increasing heat and pressure, the minerals reorganize into light and dark bands, dark containing the mica and light containing the quartz. This rock is a gneiss. Then finally as we apply heat and pressure, the minerals cannot rearrange anymore, so the rock melts and forms a granite again. We have completed the rock cycle. Now during this entire metamorphic process I have described, some water that was trapped with the sediment and in some of the minerals is given off. This water with dissolved chemicals is transported away from the location where the heat and pressure is being applied. Then it encounters different physical and chemical conditions and becomes chemically unstable depositing minerals in cracks and fractures that it passes through. This is how the quartz veins from Arkansas formed. But that's not the end of the story for quartz. When a granite composition magma is intruded into a region, silica-rich fluids often go off of the magma as it crystallizes in the ground. These fluids care their dissolved minerals out into nearby cracks and fractures and form quartz veins, just like the metamorphic fluids. Usually the igneous origin fluids from granites may carry metal values, such as gold or silver or both.
What I have described for quartz crystals and quartz veins is but two processes by which quartz may form -- from molten rocks and from hot fluids. But quartz in the form of chert, flint, agate, etc may also form from cold water. Notice that I said above that quartz is normally stable in the weathering environment. Quartz is soluble in alkaline environments, like are commonly encountered in limestone and dolostone terranes. In this instance, fine-grained quartz may form as nodules in pockets or voids by the deposition of colloidal silica, which slightly recrystallizes over time. Also, in some instances like around Herkimer County, New York, nice crystals of quartz may form in these pockets from cool waters. So here is another way quartz may form!
Notice that I keep talking about quartz only. That's because books have been written about all the different ways minerals can form. Minerals exist under certain conditions. These conditions are defined as their stability fields, i.e. the range of temperatures and pressures that the minerals remain stable and do not break down. Most mineralogy books give these parameters.
Is it the same for most other crystals as well? I can't seem to find the answer to this. I am assuming that all crystals can form in any of the rock stages - provided the right elements are present. Is that accurate?
No, not so accurate. I think now you understand that not only do you have to have the right chemicals present, but also the right set of conditions of temperature and pressure. Oh yes, I forgot to mention about time. Time plays as important a role as temperature and pressure, because without significant time, the reactions don't happen and the minerals do not form. These are not instantaneous changes in minerals I have been talking about, but changes that take time to occur. Migrating elements through solid rock or even with some fluids takes a while geologically.
I would like to give you another example of how a single element exists as two minerals. Carbon. Carbon held at a temperature of 1700 degrees F and under a pressure of several 1000 lbs./square inch becomes the mineral diamond. The elemental carbon is packed as atoms as tightly together as is physically possible. How can a mineral formed under such conditions exist at room temperature and pressure? Well, if it was transported rapidly to the present conditions, then it has the inclination to alter to graphite, but did not have the time! Mineralogists call diamond a meta-stable mineral. Contrary to what DeBeers advertizes, diamonds are not forever! Now diamonds crystals that are transported slowly to the earth's surface are dissolved by the transporting material and disappear if the material they are traveling in reaches the surface too slowly. Graphite is the stable form of carbon under the conditions that exist on the earth's surface and in the earth's crust. Only in the mantle do the necessary conditions exist for diamond to have formed. Now, let's take organic carbon, trapped in a sedimentary rock and plunge that rock into the upper mantle. That carbon will first be converted to graphite on the trip down to the mantle and then to diamond as it encounters those conditions of heat and pressure necessary for diamond to form. If we then slowly bring that mass of ultrametamorphosed rock back to the earth's surface, then the diamond present in that rock will alter back to graphite, but perhaps retain the external crystal form of diamond. A piece of such a rock has been discovered and documented occuring in China. It contains graphite pseudomorphs after diamond in it!
Well I know this is a lot more than you asked for, probably you are now thinking. But you ask some humdinger questions that I can't help but try and answer!
A. Well, a crystal grows by chemical accretion. It may grow in a prefered direction due to the internal structure to produce a prismatic, equidimensional or tabular crystal form. Typically, quartz is prismatic, galena is cubic or octahedral, and barite is tabular. In these instances, growth zones indicate where the crystal is accreting most rapidly. With quartz this growth is usually on either one of the trigonal termination sets of faces. Rapid growth of the termination faces (the growth zone) causes the crystal to be elongate. Rapid growth along one of the a axes results in a tabular quartz crystal. Sometimes the growth can be more rapid at the edges of the faces (where two faces join, like the common join of a termination face and a prism face). This results in the development of a multiple termination crystal. In this type of growth the termination consists of a "hollow point" with a stairstepped hole in the middle! Now this process really has no direct relationship to phantoms as the phantom simple represents either the capture of foreign material in the crystal as it was growing or another type of process mentioned below. Typical examples of captured minerals which form phantoms are shale particles or chlorite. Phantoms may also be caused by any mechanism which alters the continous growth process, such as drying out of the pocket, changes in the chemistry of the fluids supplying the growing crystal, earth movement, etc. Any of these processes which cause a change in the fluids may result in various types of phantoms: white capped phantoms ( the growth of a milky termination which then is covered with a growth of colorless rock crystal), white cloud phantoms (early growth of a milky crystal which is then coated with a later growth of rock crystal), or "ghost" phantoms which usually only consist of a pale phantom displaying only the termination faces. This latter type may be due to the drying out of a pocket and then resaturation with fluid. Tiny gas bubbles might adhere to the termination of the crystal, being incorporated as an almost invisible termination cap. I have seen this in examples from Brazil which have as many as 5 of these types of phantom terminations in an individual crystal.
So I don't know if I answered your question about growth zones, which are either faces or edges and phantoms which display the early shape and form of the crystal during some stage in its growth.
Q. We were in Hot Springs, Arkansas a couple of weeks ago, and of course had to go to Mt. Ida to dig quartz crystals. We were staying with a friend who knows a mine owner and we had a wonderful time. It happened to be a record setting temperature day of 105, but we started at sunrise and were exhausted by 11:00. While I was buying some oxalic acid in one of the local rock shops, I saw some really interesting examples of coontail quartz. Even though I have heard of this quartz before, this was my first time to really get to examine some. I bought a small piece and of course its location was given as Magnet Cove. Could you give me some information on how and what gives this quartz its strange appearance?
Thanks and Happy Hounding,
A. Coontail quartz is a local name for a particular variety of smoky quartz collected at several sites adjacent to Magnet Cove. Examples are known from the Hardy-Walsh property, Moses Hill, and the Christy mine, but perhaps the best known and most collected site was the Runyan quartz mine, which was located on a novaculite ridge about a mile due north of the Magnet Cove intrusion.
The best examples of coontail quartz are characterized by sector growth and some alternating zoning of both smoky and milky gray quartz. Individual crystals rarely are seen over 1.5 inches in length, but they might reach the same size in diameter. In other words, they are generally short and stubby in habit rather than long and prismatic like the more typical rock crystal variety of quartz. Coontail quartz gets its name from the alternating color bands sometimes seen on the exterior of crystals, which may somewhat resemble the pattern of a racoon's tail. This banding is also readily seen if you cut and polish the crsytal at right angle to the point or termination. I cut several cabochons and they all display this zoning very well. Another characteristic of coontail quartz from the Runyan mine is that the surface luster is usually dull, even on the termination. This is probably due to late alkaline fluids having etched the surface.
Mr. Carl Runyan operated this mine for a few years, before he passed away. Then his widow let a relative operate it for awhile. He produced a large amount of coontail quartz which he sold to Ron Coleman. Ron still has it for sale at his two shops, principally the shop called Rocks-R-Gems on US Highway 270 East in Hot Springs, near the federal Gulpha Gorge campground. The site has been closed to private collectors since Mr. Runyan's death. It is interesting to note that this is the furthest site away from the Magnet Cove intrusion that shows this type of mineralization associated with escaping fluids.
The dark gray to sometimes black quartz formed in fractures in the white hard Arkansas Novaculite formation. The smoky color was due to irradiation effects. Mr. Runyan told me that he initially located the veins on the ridge with a geiger counter. The AEC checked out this location years ago and all the radioactive material here was thorium-bearing, not uranium so there was no commercial interest in the location until Mr. Runyan came along. The mine consisted of a series of bulldozer cuts, trending along the length of the ridge. In the cuts where the best quartz veining was exposed, a trackhoe was used to break out the specimen material. The veins I have seen in place were exposed for several feet and trended parallel to the east-west trend of the ridge. Some minor crossveining was also present. The largest veins I saw had up to 4 inch wide cavities with crystals projecting inward. The site is known also for the extremely tenacious iron-cemented clay that coats the crystals and causes a real problem in cleaning specimen material. I also saw and collected some few specimens of sparkly smoky quartz drusy crystals (very attractive micromount material), some late crusts of drusy rock crystal on top of the stubby coontail growth, and some very small, but highly lustrous black brookite crystals and druses of these brookite crystals. I have seen essentially none of this type of material at the local rock shops in Hot Springs, only the more typical zoned coontail on novaculite matrix from the Runyan mine. One shop at Mount Ida has some clusters of small doubly terminated, dull lustered, grayish quartz from the Christy mine that they are calling "alpha" quartz. It's not alpha quartz, but instead normal gray smoky quartz that formed as coarse druses in some zones in the novaculite, but it is somewhat attractive and unusual now that this Christy mine has been reclaimed.
There is still a significant amount of coontail quartz available at local rockshops! I heard that one fellow in Hot Springs Village had actually purchased enough of this rock to have a fire place built. I think that might be pretty impressive to see, but so far have had no luck finding this person.