Shandite

Shandite
General
Category	Sulfide mineral
Formula (repeating unit)	Ni3Pb2S2
Strunz classification	2.BE.15
Crystal system	Trigonal
Crystal class	Hexagonal scalenohedral (3m) H-M symbol (3 2/m)
Space group	R3m
Unit cell	a = 5.59 Å, c = 13.57 Å; Z = 3
Identification
Formula mass	654.60 g/mol
Color	Brass yellow, cream-white in polished section
Crystal habit	Generally found as an inclusion
Cleavage	{1011} Perfect
Mohs scale hardness	4
Luster	Metallic
Diaphaneity	Opaque
Specific gravity	8.72
Birefringence	Strong, dark blue-gray
Pleochroism	Distinct
References

Shandite is a sulfide mineral with chemical formula: Ni₃Pb₂S₂. It was discovered in 1950 and named after Scottish petrologist, Samuel James Shand (1882–1957). It is characterized by a metallic luster and a brass-yellow color. It has a specific gravity of 8.92, and a Mohs hardness value of 4. Shandite is commonly found as an inclusion in other minerals such as serpentine.

Its crystal system is trigonal hexagonal scalenohedral with symbol 32/m. It belongs to the space group R3m. Shandite is an anisotropic mineral, which means it has different properties when being viewed from different directions. In cross-polarized light it appears as gray blue or yellow-brown colors. It also has very distinct relief, which means it stands out against its mounting medium and can be easily seen. It has an index of refraction of 1.54, which is the measure of the speed of light through the substance. In plane polarized light, shandite has a creamy white color and distinct pleochroism, which is the property that makes it appear to be different colors at different angles. It has strong birefringence, which is the decomposition of light into two rays, and appears dark blue and gray.