Turquoise Information

Turquoise is a hydrous phosphate of aluminum and copper, Al2(OH)3PO4 H2O+Cu. Stone Mountain Turquoise on the other hand has very unique combinations of minerals that produce many colors, shapes and sizes of turquoise. The rock formations in the area have been well studied. Andesite-rhyolite, limonite, porphyry iron, hornblende quartz monzodiorite, argillaceous, and carbonate sedimentary rocks including evaporates are found there.

These rock formations went through many earth changes throughout prehistoric periods. Some were gradual and others abrupt and violent. Blended rock formations that appear to be burned, melted then pressured into to a crystalline structure. We also found formations appear as “mineral vugs”. There were however two consistent types of turquoise, “turquoise nuggets” and “vein turquoise“.

Vein Turquoise: A good majority of the turquoise found at Stone Mountain is “vein turquoise”. Thickness of the stones ranges from 1mm up to 30+mm in larger slabs. A fairly common dimension for vein turquoise from Stone Mountain: 25x30x3-4 mm. Adding that there are always a large amount of smaller vein pieces of varying size.

Nugget (Vug) Turquoise: Near 20% of the stones found are turquoise nuggets. Turquoise nuggets form in pockets of softer hostrock and precipitate clays that sift into cracks and voids within the host rock outcropping in all parts of the claim. A common shape and size for our nugget turquoise is 29x20x6-10 mm. Smaller nuggets in a variety of sizes are scattered in a wider range. Some of the turquoise nuggets came from a narrow voids and so they are mostly flat in dimension but still retain a bumpy surface. We like to call these “vein nuggets”.

Botryoidal Turquoise: (rare nugget form) Another rare form of turquoise found at Stone Mountain Mine is “Botryoidal Turquoise”, this type of turquoise is formed by Botryoidal Crystal formations that form in larger cracks and mud veins where the cracks or voids are large enough so that when the turquoise is forming it swells evenly in a near 360 degree radius. Naturally the turquoise crystal form like a “bunch of grapes” in appearance. The rich mineralized clays that fill these voids and cracks cause a great deal of pattern and color variety in the turquoise. The majority of this type of turquoise is considered to be Sub-Botroydial, because the stone was restricted in shape on one or more sides of the stone. Some of this interesting material resembles a frog skin or toad skin texture.

Translucent Turquoise: (Rarest Form)

In our opinion this is the finest grade material we have ever seen! The translucent turquoise is absolutely remarkable! In general in runs in thin veins of varying colors, a good majority of the translucent material is a beautiful Blue-Green color. Much of the translucent turquoise runs within cracks in vicinity of large bodies of quartz that are speckled throughout the deposit. There is always an exception and we sometimes find translucent material that is botroydial, has quartz matrix or even a block like shape. in 1987 a Gemology was performed by the late Allen E. Lombardo. He found that our midgrade material had varying translucence. This was an interesting discovery for us, and since that time we have discovered a larger variety of translucent material. Hold one of these slabs up to your standard desk lamp and you will see what we mean.

Reference Sources:

Turquoise Mineral Data
Area Mineral Findings
Mineral Vugs
Botryoidal Crystals
Sub-Botroydial
Plagioclase Feldspar
Porphyritic Quartz Monzodiorite
Intrusive & Extrusive Quartz

Allan E. Lombardo Gemology – Page 1 – Page 2 – Page 3
To see the type of turquoise used in this gemology click here