Chalcopyrite

Chalcopyrite

COLOR

Pure yellow. Polishes easily. No pleochroism has been observed.

REFLECTANCE

Rather high. Much like that of galena. By direct comparison, slightly higher. Lower than pyrite.

ANISOTROPISM

Weak to extremely weak. By slightly uncrossing the nicols, yellow-brown to bluish grey or greenish grey tints appear.

TEXTURE

In almost every specimen, polysynthetic twins are observed. The mineral contains frequent sphalerite, sometimes stannite exsolution, both as characteristic lace-like four-pointed stars. Also cubanite lamellae and flames of mackinawite. These flames are sometimes replaced by pyrrhotite. All these exsolution textures suggest relatively high deposition temperatures (about 300 °C). However, it seems to be established now, that mackinawite implies lower temperatures. Sometimes, cubanite lamellae have completely disappeared and are replaced by chalcopyrite. The occurrence of pseudocleavage in chalcopyrite, corresponding to the outlines of primary lamellae, is diagnostic of the former presence of cubanite.

ASSOCIATED MINERALS

All the metallic minerals but especially: pyrrhotite, galena, sphalerite, pyrite, cubanite, stannite, and arsenopyrite.

CRITERIA OF DETERMINATION

The pure yellow color is diagnostic. Only gold has such a yellow tint (even yellower), but its reflectance is extremely high and polishes rather poorly. Misidentification can occur for minute grains only.

Source

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