CATTIERITE
Cattierite – CoS2 – is a very rare sulfide and, consequently, of no importance as an ore.
It is classified within the Pyrite Group, forming a series with pyrite and another with vaesite (NiS2). Thus, it may contain varying amounts of Fe and Ni, as well as Cu.
1. Characteristics
Crystal system: Cubic diploidal.
Color: White-gray, pinkish, brown.
Habit: Massive, granular, cubic crystals up to 1 cm, intergrowths.
Cleavage: {001} perfect.
Tenacity: No information available.
Twinning: No.
Fracture: No information available.
Mohs Hardness: 4
Parting: No.
Streak: No information available.
Lustre: Metallic.
Diaphaneity: Opaque.
Density (g/cm³): 4.82
2. Geology and Deposits
Cattierite occurs in carbonate rocks associated with U-Cu-Co-Ni-type ores.
3. Mineral Associations
It occurs associated with pyrite, chalcopyrite, magnesite, minerals of the linnaeite-polydymite group, and especially erythrite.
It generally occurs in granular intergrowth with another mineral of the linnaeite-polydymite group. It never occurs alongside vaesite in the same vein.
4. Transmitted Light Microscopy
This does not apply, as cattierite is completely opaque.
5. Reflected Light Microscopy
Sample preparation: The polishing hardness of cattierite is slightly higher than that of sphalerite.
PLANE POLARIZED LIGHT – PPL
Reflection color: White, with a subtle pinkish tint. The pink hue is diagnostic.
Next to galena, it appears yellowish; next to pyrite, it appears bluish.
Pleochroism: No.
Reflectivity: 38.85%
Bireflectance: No.
CROSSED POLARIZED LIGHT – XPL
Isotropy / Anisotropy: Isotropic.
Internal reflections: No.
May be confused with: siegenite (CoNi2S4), but its reflection color is even more pinkish.
General Characteristics:
Perfect cubic cleavage may be clearly visible, but only in larger crystals.
Substitution of cattierite by pyrite can occur. It may be replaced by pyrite and siegenite (CoNi2S4).
Cataclasis is possible.
Intergrowths with pyrite and galena occur.
