Chalcocite (Weight: 136.31 g) – Place of discovery: St. Just, Cornwall, England — Photo: Raimond Spekking · CC BY-SA 4.0
Chalcocite
Also known as: Copper glance.
Copper(I) sulfide — a dark-gray to black metallic copper ore with a Mohs hardness of 2.5–3.
Intro adapted from Wikipedia (CC BY-SA).
Chalcocite is an IMA-recognized mineral species in the sulfide class, with the chemical formula Cu₂S.
It crystallizes in the monoclinic crystal system (space group P2_1/c).
Key properties: Mohs hardness 2.5–3; specific gravity 5.5–5.8; typically gray or black; Blackish lead-gray streak; Metallic. Anisotropism: Weak. R1 –R2: (400) 37.0–36.8, (420) 37.8–37.4, (440) 37.7–37.6, (460) 37.0–37.2 luster.
IMA symbol Cc, grandfathered status — known before the IMA’s founding.
An uncommon primary hydrothermal mineral but important as a secondary mineral. Found in or below the zone of oxidation in hydrothermal veins and in large low-grade porphyry copper orebodies.
It is found associated with Pyrite, chalcopyrite, covellite, bornite, molybdenite, many other sulfides and their alteration products.
The name refers to its composition, from the Greek for chalkos, copper.
Collections: Metals & Native Elements.