Mineral Factbook

Acanthite

Ag2SIMA symbol: Acagrandfathered

Acanthite is a sulfide or sulfosalt mineral with the formula Ag2S, crystallizing in the monoclinic system. It has a Mohs hardness of 2-2.5, typically black in color, with a metallic luster, a specific gravity of 7.2-7.3. Its streak is black.

Photos

Acanthite specimen photo
Pacific Museum of Earth from Canada · CC BY-SA 2.0 · Commons
Acanthite specimen photo
Pacific Museum of Earth from Canada · CC BY-SA 2.0 · Commons
Acanthite specimen photo
Pacific Museum of Earth from Canada · CC BY-SA 2.0 · Commons
Acanthite specimen photo
Pacific Museum of Earth from Canada · CC BY-SA 2.0 · Commons

Crystallography

Crystal systemmonoclinic crystal systemWikidata (CC0)
Space groupP 1 21/n 1
Cell (Å, °)a = 4.229, b = 6.931, c = 7.862; α = 90, β = 99.61, γ = 90
Cell volume227.211 ų, Z = 4
Axial ratios0.6102:1:1.1343calculated from COD 9000253
Source structureCOD 9000253 (American Mineralogist, 1971) — 1 of 2 structures

Powder X-ray diffraction (calculated)

2θ (degrees, Cu Kα1)I/I₀ (max 100)
d (Å)2.6072.4422.5832.3822.8373.082
I/I₀10077.170.96965.660.3

xrd-v1: CuKa1 1.5406A, 2theta 5-90, top10, Imax=100, no DW/PO. Computed from COD 9000253; idealized occupancies, no preferred orientation.

Physical properties

Density (calculated)7.244 g/cm³calculated from COD 9000253
Hardness (Mohs)
2-2.5single sourceDana, System of Mineralogy, 6th ed. (1892)
Specific gravity
7.2-7.3 g/cm3corroboratedDana, System of Mineralogy, 6th ed. (1892)
Color
blacksingle sourceDana, System of Mineralogy, 6th ed. (1892)
Streak
blacksingle sourceWikidata (CC0)
Luster
metallicsingle sourceDana, System of Mineralogy, 6th ed. (1892)

Chemistry (calculated)

Molecular weight247.8 g/molcalculated from the IMA formula
Composition (wt%)Ag 87.06%, S 12.94%

Classification

Nickel-Strunz (10th)2.BA.35Wikidata (CC0)
Nickel-Strunz (9th)2.BA.30Wikidata (CC0)
Dana (8th)2.4.1.1Wikidata (CC0)