Mineralpedia Details for Tennantite

Named to honor Professor Smithson Tennant, a chemist of Oxford University at Oxford, England. Tennantite occurs in deposits metamorphosed by contact metamorphism as well as in hydrothermal veins. Found in over a thousand localities and related to tetrahedrite, but is more rare than tetrahedrite.

Ref. Handbook of Mineralogy, Anthony et al (1995) and MSA at http://www.handbookofmineralogy.org/pdfs/tennantite.pdf

Formula

Cu₁₂As₄S₁₃ 

Crystal System

Isometric 

Crystal Habit

Massive - Granular, Massive, Disseminated 

Cleavage

None, None, None 

Luster

Metallic 

Color

steel gray, black 

Streak

reddish gray 

Class

Isometric - Hextetrahedral 

Fracture

Hackly 

Hardness

3.5-4 

WebMineral

View Tennantite 

Mindat

View Tennantite 

2mm tetrahedras which are rimmed with perhaps a different mineral, possibly Chalcocite. The cores are a brilliant silver, while the rims are a brassy chalcocite color and the outer rim is a dull, pitted, black or dark grey. There are numerous minute clusters of Quartz about the matrix.

Crystal group with individual crystals to 6mm.

An interesting specimen with hundreds of well developed crystals to 1mm on sulfide matrix. The cavity on which the crystals have formed is large and is 6x5cm across and composed mostly of Chalcocite. The rest of the matrix is sulfide, probably Chalcopyrite There is also some vugs on the backside.

Two good Tennantite crystals - 1.9 and 1.4cm.