Athabascaite

COLOR

Grey-blue with a very strong pleochroism ranging from faint light grey to darker grey-blue. It is similar to covellite but greyer and pleochroism is not as strong. Takes a good polish.

REFLECTANCE

Medium. In the lightest position, a little darker than eucairite.

ANISOTROPISM

Quite strong to extremely strong in very bright yellow tints. Under crossed nicols, the tints range from bright yellow to orange-yellow.

TEXTURE

In the specimen studied, the mineral was seldom independent, forming myrmekitic intergrowths with eucairite.

ASSOCIATED MINERALS

Eucairite, clausthalite, other selenides, pitchblende, chalcopyrite.

CRITERIA OF DETERMINATION

Because of its pleochroism and very strong anisotropism can be confused only with klockmannite and covellite. Klockmannite is more distinctly green-grey (brownish in oil) and polarizes in less distinctly yellow tints. Covellite is much bluer and polarizes in brighter orange colors. However, some selenium-rich covellite has optical characteristics very similar to athabascaite.

Source

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