Sphalerite

Sphalerite, also known as blende, is an important ore of zinc. It is usually very dark brown to black in colour, but occasionally, transparent yellowish brown or green stones are found that can be faceted. Since sphalerite is soft and has perfect cleavage, it is not suitable for jewellery, and is faceted for museums and collectors only.

Sphalerite crystals are usually pseudo-octahedral in shape, forming in hydrothermal veins with other minerals, such as galena, quartz, pyrite and calcite. Transparent, cuttable stones are found in Santander (Spain) and Mexico.

In the past, sphalerite has often been confused with galena (lead sulphide), to which it is similar.

Sphalerite Pictures

Sphalerite and quartz crystals

Sphalerite Properties

Chemical Composition: 
Zinc sulphide
Crystal System / Forms: 
Cubic
Hardness: 
3.5
Specific Gravity: 
4.09
Lustre: 
Metallic to vitreous.
Refractive Index / Birefringence: 
2.36-2.37 / None.
Magnification: 
In cut stones, high fire shows rainbow colors.
Sources: 
Santander (Spain) and Mexico.
Cuts & Uses: 
Brilliant, Mixed.