Monday, April 25, 2011
Turquoise and The Colorback Mine
One of the most recognizable gemstones to anyone in the world is the blue stone turquoise. There is not another like it. It has become the symbolic color and gemstone of the American southwest. Its history starts in ancient Egypt where it was mined on the Sinai Peninsula. Later Prussian turquoise was mined as a solid sky blue and Tibet turquoise is wondrous blue-green and is so sacred it is considered a national treasure. More recently, the Native Americans of the southwest have mined it in many shades of blues and greens.
In the 1950’s to the 1970’s turquoise was highly prized and sought after by consumers. It was to the point that a poor prospector could find a new deposit and be wealthy beyond dream within months. By the mid-1970’s turquoise was loosing favor with consumers and the demand dwindled to a small trickle we see today. There is still some demand for high quality gem material with jewelers and mineral collectors but not enough to cause the huge price spike from the 1970’s.
In recent years the demand has increased. Much quality turquoise, like at the Colorback Mine, sell for as much as a $1000 per pound or more. That’s nearly $70 per ounce or $1.80 per carat. Carat per carat this price doesn’t seem like much when comparing prices to a diamond. That shouldn’t diminish the value of turquoise as its beauty far exceeds the beauty of a clear diamond.
Colorback Mine I and II:
The Colorback mine I or in the old days Turquoise Boy mine is one half mile north of the famous Badger mine (another famous turquoise mine) and 3.5 miles North-Northwest of Tenabo (a mining district & ghost town known for its gold) just south of Crescent Valley, Nevada.
Turquoise is associated with an opalized sill that dips intruding black chert. The chert adjacent to the sill is brecciated and that is where the turquoise was formed.
The Colorback II mine has more Chalcosiderite and Variscite rather than turquoise as the major constituent. The Chalcosiderite has a beautiful black spider web pattern with white, blue, green, yellow, or orange hues.
The variscite is a beautiful light green to “icy” green with black spider webbing or matrix throughout the stones.
Much of the material from this mine is a mix of turquoise, variscite, and chalcosidierite. An easy and fairly reliable way to determine what you have is by color. If your stone is more blue it is predominately turquoise. If it is more of a strong green it is predominately variscite and if it is pale green or whitish then it is predominately chalcosidierite. However, on the gem market it is usually ALL sold as turquoise.
Mixing of minerals like this is not uncommon. Much of the turquoise from around the world is a mix of turquoise and other minerals.