Sorry, There's no Recoverable Gold in Arkansas
Q & A Gold in Arkansas
Q. My grandfather once told me about a lost gold mine in Arkansas. Where could it be?
A. Many grandfathers tell stories about lost gold mines in Arkansas and elsewhere. Grandfathers are very good storytellers, but too many people take what they say as the truth. Even more than grandfathers, other collectors and schemers tell (and even publish!) stories about the Arkansas Gold Mines.
If your grandfather's lost gold mine was in Arkansas, then it is still lost because there has never been any production of gold recorded in the state.
There have been two gold rushes here, one a little over a hundred years ago in the 1880s, that resulted in a whole lot of people losing money in a series of wild stock investment schemes (to the tune of $113 million !!)
The second gold rush was recent, in the 1980s, when some prospectors filed over 4000 claims in one county in the Ouachita Mountains. History repeated itself, and a lot more people lost their money. Many unfortunate investors signed ironclad, impossible-to-meet contracts, and forked over their life savings to these charlatans, who have so far managed to beat all lawsuits and claims against them. I was involved with sampling "high grade ore" from some of their claims, and the laboratories found less gold than seawater has in it- less than 2 parts per billion. That's not much at all!
The moral of the story is, gold mines usually make money for somebody else...
Q. I'd like to know more about the relationship between gold and quartz. I've heard quartz is often used as an indicator mineral for gold. I'm guessing this has something to do with the densities of each mineral, both being heavy, and think maybe they tend to migrate to the same areas on the ocean floor. I'd like to know the official version and also why there isn't gold in them thar Ouachita Mountains. John.
A. John, The densities of the two materials, quartz and gold, are as different as night and day! Quartz is around 2.6 and gold ranges between 12.5 to as high as 15, depending on how much silver is present. The less silver, the closer to 15. I don't understand what you mean about migrating to the same areas on the ocean floor. This has nothing to do with the formation of either gold-bearing or non-gold bearing quartz veins.
The article I sent you explained that quartz veins form from hydrothermal (hot water) solutions. These solutions formed at some depth and migrated toward the earth's surface. As the chemical and physical conditions of the fluids changed during the migration, conditions became favorable for the deposition of quartz -- quartz crystallized from the fluid in pre-existing fractures in a host rock, usually sandstone or shale.
The origin of the fluids is the key to understanding why any quartz veins in a region contain or lack gold. The fluids must contain the gold to bring it in and have it precipitate or crystallize in the veins with the quartz.
Now, let's consider some quartz veins from various localities in the USA. In certain regions of California and Colorado, the igneous rock type called granite intruded the country rock. Coming off of these granitic igneous intrusions were late hydrothermal veins rich in dissolved silica and metals. Many of the "mother lode" type of gold deposits discovered in these states are directly attributable to such an origin. Weathering of vein deposits releases the gold to be concentrated in stream, river, or lake deposits as placers.
In Arkansas, we have had no intrusion of a granitic type of rock. We did have intrusions of a silica-deficient igneous rock called syenite (Magnet Cove, Potash Sulphur Springs, and Granite Mountain) and an ultramafic rock termed lamproite (Crater of Diamonds) during the Cretaceous Period some 100 million years ago. But the bulk of the quartz veins in the Ouachita Mountain region were deposited some 245 million years ago, and since we do not have any igneous rocks that date from that period, the veins can not be related genetically to igneous rocks.
So the real question is how did the fluids form and where did they come from? Well, we know that around 245 mybp, the Ouachita orogeny (mountain building process) was peaking in activity and then finished. Although we do not see any significant quantity of true regionally metamorphosed rocks on the surface in the Ouachitas, just over the stateline into Oklahoma there was a 10,000 foot test hole drilled for oil in McCurtain County, OK. A geologist logged this hole and described the rocks he saw. From a depth of 2,000 feet to the total depth of the hole, he described metamorphic rocks of greenschist facies. This means that from 2,000 to 10,000 feet these rocks had been subjected to elevated heat and pressure. When this occurs, certain predictable changes happen to the minerals that compose the rock. Clay is converted to mica, silica recrystallizes, and water is mobilized. In fact, you might think of progressive regional metamorphism as the dewatering of the rock.
As the temperature and pressure go higher, more and more water is removed -- until the rock finally melts and essentially becomes an igneous rock again. This is part of the rock cycle, well described in many textbooks. Anyway, the water that is expelled goes toward the surface because it is lower pressure. All fluids migrate toward lower pressure. The water is not pure -- it contains many dissolved substances and, in most instances where the original rock was deposited from the ocean, the water contains a great deal of salt. Silica is highly mobile in a salty environment and readily dissolves in the water. As this "hydrothermal" fluid reached a lower pressure and encountered open fractures, it dropped its dissolved minerals, principally quartz, although in Arkansas, we also have zinc, lead, mercury, antimony, silver, and other minor sulfide minerals deposited in some of the quartz veins. But, gold never apparently made it into the system. To mobilize gold chemically, you have to have some highly complex fluids, like those coming off of granites at the end of crystallization of the magma, and the magma has to contain the gold to begin with. It doesn't just appear out of thin air.
So Arkansas quartz veins formed from a fluid that had a different origin than the gold-bearing fluids that deposited the famous gold-quartz lode deposits of other places. That's the ultimate answer to your deceptively simple, but highly complex, question. Mike H.
Q. I've heard that there was an old gold area in Arkansas referred to as "The Old Spanish Diggings." Is this fact or just another "tall tale?"
A. It is no tall tail that there is an area referred to as the Old Spanish Diggings, but there is no evidence that the Spanish ever visited the site, much less did any digging there. According to Theo B. Comstock, who was a geologist that studied the many "gold mines and claims" in the late 1880's, the area by this name consisted of a number of bog iron and manganese deposits on the side of a hill. These deposits were formed by cold water spring seeps over a period of time and had bowl-like shapes. They had no evidence of any digging by anyone, but apparently the local people thought the Spanish had dug them because of the shallow depressions. Anyway, so much for another gold discovery in Arkansas. As with many of these stories, there is a grain of truth -- in this case the name, but anything else concerning gold and the site is purely imagination.