This article came to be when I offered Bob some digital images of Graves Mountain in Lincoln County, Georgia. He asked for a collection oriented companion text and that lead to the specimen images and the words that follow. It’s all from the perspective of a guy who’s a devoted amateur collector, geologist wannabe and a field trip just waiting to happen...
At left, a view southward across the main pit from the roadway. The light brown water is a occasional rain pool . It has been eliminated by a drainage ditch that carries water into the pond formed by the damming of the lower pit, which is the darker brown water in the center of the picture. At center, looking into the main pit from the road. At right, looking westward from inside the main pit.
The geological history of Graves Mountain is as complex as the rest of the eastern seaboard. To make a complicated hundreds of millions of years story simple and short, a super continent broke up, the pieces drifted apart creating an ocean and volcanic island chains. The pieces came back together, sweeping up the island chains along the way and forming another super continent. This super continent broke up as well and the pieces drifted away to form our present day continents and the Atlantic Ocean.
Geologists still debate the exact details but certain aspects are clear. Sometimes during the continental collisions the Graves area was subducted and subjected to heat and pressure under the earth new minerals were formed, existing minerals were altered. There were many episodes of metamorphism when the rocks were heated and sometimes fractured and secondary minerals formed and filled the fissures. As the heat and pressure varied, different minerals were formed and underwent metamorphism. Eventually the area was raised back near the surface and eroded to its current exposure.
At left, the northern wall from inside the main pit. The road into the pit runs along the top of this wall.
It’s not much of a mountain, rising only 500 or so feet above the surrounding terrain. The rise is gradual and the tall pine trees block your view, so it’s only when you're on the mountain itself that you realize just how high up it is. It seems strange to be in a giant 100 plus foot deep hole and still be able to look out across a forest canopy below.
Graves Mountain became a famous mineral location in the 1800s and collectors dug prospects around the area. Eventually it became a kyanite mine. A large main pit was dug in the heart of the mountain. Two smaller pits were dug above and below that. Ultimately the mine was shut down as other materials replaced kyanite in industrial usage and mining became less profitable.
At right, the east wall of the main pit.
If there is a theme to Graves Mountain it is “change”. The same minerals come in many different conditions or have been altered to other minerals. The reasons why are varied. The area underwent many episodes of metamorphism, many of the minerals don't seem to be stable long term under surface conditions and material is now exposed to weathering and chemical weathering.
Pyrite is ubiquitous throughout the area and some of it decomposes into the original iron and sulfur. The sulfur in turn is swept up by the rainfall and the ensuing pools and runoff are acidic. This has lead to litigation between the owners and surrounding neighbors. Periodically baking soda is dumped to neutralize the acidity. The lower pit has been dammed to help control the water flow.
Because the mine is inactive the glory days are over as no new material is uncovered. Nowadays you can only collect what is exposed by erosion or what you or somebody else digs or sledge hammers out.
A collector could reasonably expect to find the following minerals…
Quartzite: Quartzite is a common base rock. Very hard and light gray in color, it may include small pyrite, lazulite, quartz, kyanite and vugs of micro minerals. The quartzite is very subject to weathering and can be found in all stages from the original hard stuff to sand grains barely clumped together.
Quartz: This most often occurs as seams of massive milky quartz. At times this will include pyrite crystals, small blobs of rutile or rutile crystals. Quartz crystals formed in pockets but these seemed to have all been broken up or slagged in subsequent events. Remnants as thick as a forearm are sometimes found but are nearly unrecognizable as crystals. Often they are coated with hematite and iridescent hematite.
At left, blobs of rutile on kyanite matrix. Kyanite is weathering to silvery 'mica'. Specimen approximately 2 inches.
Kyanite: This is not the long blue bladed material typically shown in field guides. This kyanite is short thick tabular crystals in various shades of greenish blue. Kyanite also formed in fissures in the base rock. It may include pyrite crystals or rarely small blobs of rutile. The kyanite is commonly associated with the massive quartz and/or quartzite. The kyanite seems to be particularly susceptible to metamorphism, weathering and chemical weathering. Sometimes a single specimen can show all sorts of transitions to other minerals. One of the most common is a very flaky silvery “mica”.
Pyrite: Pyrite is mostly in the form of very small crystals as inclusions or coating other minerals.
Above left, lazulite in quartzite. Specimen approximately 8 inches. Above right, close-up of a lazulite crystal in weathering quartzite. Specimen approximately 2 inches.
Lazulite: Crystal of dark deep blue lazulite sometimes occur in the quartzite. These are inseparable from the host rock. This material does slab, cab and polish well. As the quartzite decomposes into sand, the lazulite crystals begin to free up and show distinctive faces and change shade to a paler blue.
At left, close-up of white and burgundy pyrophyllite crystals with a rare coating of blue pyrophyllite. Specimen approximately 12 inches.
Pyrophyllite: Stellate crystals of pyrophyllite also formed in seams. Throughout the mine it can be found as coatings on other rock. Mining sometimes dislodged the larger seams as pyrophyllite boulders. Pyrophyllite is itself very soft and is sometimes used in lieu of talc, interestingly the boulders of massive pyrophyllite crystals are very hard and it’s difficult to chisel them into manageable pieces.
Above left,ten plus rutile crystals in a metamorphosed kyanite matrix. Crystals were nearly totally buried under metamorphosed mica like kyanite. Specimen approximately 6 inches. Above right, twenty plus rutile crystals in a quartz, metamorphosed kyanite matrix. Several crystals appeared to be covered by a film of 'rust' . Specimen approximately 6 inches.
Above left, loose rutile crystal with over eight faces and a small penetrating 'crystalette'. Three 'sides' with no faces. Specimen approximately 1 inches. Above right, loose rutile crystal with over eight faces and several sides with no faces. Specimen approximately 1 inches.
Rutile: The number one prize of collectors, rutile most commonly occurs as shiny metallic black crystals often having a slight reddish hue. The crystals come in all sorts of shapes, penetrations and clusters. The rutile is often associated with multiple matrix rock with a large quartz and metamorphosed kyanite content. It may also occur in the massive milky quartz. Crystals in these matrixes have a tendency to pop out of the host rock, thus loose crystals may be most common. Often they leave behind a thin layer of the crystal face called a “cap” in the host rock. Some rutile also occurs in a hard mixture of quartz and kyanite that is white and pale blue in color. In those early days and when mining was active, huge forearm sized crystals and giant clusters were not uncommon. Those days are long gone and any rutile is a treasure. Sizes now run from micros up to about 2 inches. I've seen a handful collected in the 4 inch range. It’s not unusual for crystals to appear to have been broken apart and then reset at a not quite right angle.
Ilmenite: Ilmenite occurs as black tabular plates that for all the world resemble a hard metallic mica. It can be found loose or jutting out from boulders.
Above left, iridescent hematite on 'slag' rock. Specimen approximately 2 ½ inches. Above right, close-up of iridescent hematite on 'slag' rock.
Hematite/Goethite/Limonite: All three of these terms are used for the various forms of iron found at the mine. Hematite is used most often used. The most common form is hematite coating other rocks. Through weathering, this coating often becomes iridescent. The iridescence varies from a slight coloring to brilliant rainbow colors that cover small sections or entire specimens. This turns really ugly brown rocks into works of art. The best specimens come from pockets in the mine walls. Specimens can become iridescent or more iridescent by being left exposed to weathering outside in protected areas such as a window ledge. Water tends to dull or remove the color, so pieces should never be washed or left in the rain. Hematite also occurs in a botryoidal form in vugs in pyrophyllite or other rocks.
Every mineral formed in certain zones and you are still most likely to find certain things in certain places. But because vast amounts of material were moved around the mine, you are subject to finding anything anywhere.
Safety & Courtesy
Despite the heights, Graves Mountain is not an inherently dangerous location. Using the proper caution the mine is safe. Here and at all other locations, stay away from the edge, don't climb the walls, don't sledge hammer walls, don't tumble rocks down the slope when people are below you, be careful how you dig, be careful how you move boulders, be careful using hammers and wear glasses when hammering. It is a very steep, strenuous and long walk up to the mine and down into the main pit so don't try to carry too much out. A cart or hand truck comes in handy. Here as on all field trips everywhere, please use common sense and courtesy.
Collecting was prohibited for many years and the mine was only reopened in the early ‘90s. Entry is strictly controlled with the gate locked and trespassers prosecuted. To collect at the mine you need to contact and/or join one of the area clubs. Many Georgia, South Carolina and North Carolina clubs schedule trips.. Both clubs listed below go in multiple times during the year.
Georgia Mineral Society, POB 15011, Atlanta, GA 30333-5011
Cobb County Gem & Mineral Society, POB 309, Marietta, GA 30061
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