Pyrite

Pyrite

COLOR

Very light yellow. Takes a difficult polish because of its hardness. Only cassiterite, laurite, eskolaite and hematite have a higher polishing hardness.

REFLECTANCE

High. Higher than galena and chalcopyrite.

ANISOTROPISM

Usually isotropic, but most pyrites polarize weakly. By uncrossing the nicols, yellowish to greenish tints appear.

TEXTURE

Strongly tends to develop idiomorphically. Manye crystals show a distinct zoning. Pyrite also displays a tendency to develop a cellular texture resulting from the epigenetical replacement of organic tissue. It also forms spherical aggregates constituted by the association of small euhedral crystals. The significance and origin of this spherical pyrite, generally occurring in sedimentary deposits, are still unexplained. Pyrite commonly replaces pyrrhotite leaving residual inclusions. Sometimes, under oxidizing conditions (often ascending cementation) pyrrhotite is replaced by a mixture of pyrite and magnetite (or hematite) associated with marcasite. The textures thus obtained are quite diagnostic.

ASSOCIATED MINERALS

Practically all minerals but especially galena, sphalerite, pyrrhotite, chalcopyrite, arsenopyrite, marcasite, melnicovite and lead sulfosalts.

CRITERIA OF DETERMINATION

The yellow-white color, high reflectance and high polishing hardness are characteristic.

Source

ATLAS OF ORE MINERALS (P. Picot and Z. Johan)