Highest values go to finer blue colors.
The International Gem Society (IGS) has a list of businesses offering gemstone appraisal services.
|Stone Sizes||Only cabochons can be cut, up to several inches in length.|
|Colors||Blue of various shades.|
|Fracture||Uneven to splintery|
|Cleavage||Very good in 2 directions|
|Crystallography||Orthorhombic. Crystals slender prismatic; massive, granular; fibrous.|
|Absorption Spectrum||Not diagnostic.|
|Optics||a = 1.752-1.753; β = 1.782; γ = 1.815. Mean refractive index 1.75. Biaxial (+), 2V = 88°.|
|Optic Sign||Biaxial +|
|Luster||Vitreous to silky.|
|Polish Luster||Vitreous to silky.|
|Transparency||Translucent to opaque.|
a = 1.752-1.753; β= 1.782; γ=1.815. Mean refractive index 1.75.
Biaxial (+), 2V: 88°.
An alteration product of secondary copper minerals.
Shattuckite is often mixed with quartz, and data often reported for properties may be erroneous. The cabochons are rich blue in color and very popular, but the material is not abundant and seldom seen on the market.
Often mixed with quartz. Primary source Shattuck Mine, Bisbee Arizona.
Shattuckite is often confused with plancheite, which has recently been identified as a separate species, formula Cu8(Si4O11)2(OH)4 . xH20 There is no method of distinguishing between these species with common instruments. Gems must be sent to a major lab for positive identification.
From the Arizona locality, the Shattuck Mine. Recent studies have shown that plancheite, a mineral similar to and often confused with shattuckite, is a distinct species. The formula of plancheite is: Cu8(Si4O11)2(OH)4 ·Xh2O.