Aguilarite

Aguilarite

COLOR

Light grey. Very similar to argentite. polishes with difficulty because of its softness but better than argentite.

REFLECTANCE

Medium. Lower than naumannite and slightly higher than argentite.

ANISOTROPISM

Weak but visible. Similar to argentite, bluish grey with a purplish to greenish tint under slightly uncrossed nicols. Under the arc lamp, the colors are strongly purplish blue. Naumannite shows brighter colors. Unlike argentite light corrosion is practically absent.

TEXTURE

As in argentite, twin lamellae indicate inversion of cubic to aguilarite at a temperature of 133°C.

ASSOCIATED MINERALS

All the silver or Cu and Ag sulfides and selenides. Sometimes replaces galena. Associated also with native silver or electrum.

OCCURRENCES

Guanajuato (Mecixo).

CRITERIA OF DETERMINATION

The mineral can hardly be mistaken for argentite which it differs from by a slightly stronger reflectance, a better polish and especially the absence of light corrosion. Naumannite has stronger and more highly colored anisotropic (though with always the same shades) and a better polish.

Source

ATLAS OF ORE MINERALS (p. picot and z.johan)