Acanthite(alpha)

Formula : Ag2S

Family: 
Sulfides
Space group: 
Monoclinic - Prismatic H-M Symbol (2/m) Space Group: P 21/n
Dana class: 
2.4.1.1 (2) Sulfides - Including Selenides and Tellurides (2.4) where Am Bn Xp, with (m+n):p=2:1 (2.4.1) Dana Group
High temperature: 
Acanthite is stable under a normal atmospheric conditions to the weak hydrothermal conditions.
Geological context: 
Low-temperature sulfide veins and in zones of secondary enrichment. Tailings

Dernière mise à jour le 25.01.2021

THERMODYNAMICS

Individual properties (298.15 K)
M
g·mol-1
 V°
cm3·mol-1
 ΔGºf
J·mol-1
 ΔHºf
J·mol-1
 Sº
J·mol-1·k-1
 CP
J·mol-1·K-1
247.802 34.200 (Ref.: 78hel/del) Helgeson, H.C., Delany, J.M, Nesbitt, H.W., and Bird, D.K., 1978. Summary and Critique of the Thermodynamic Properties of Rock Forming Minerals: Amer. J. Sci., 278A, 229 pp. -39448 (Ref.: Internal calculation) -31589 (Ref.: 78hel/del) Helgeson, H.C., Delany, J.M, Nesbitt, H.W., and Bird, D.K., 1978. Summary and Critique of the Thermodynamic Properties of Rock Forming Minerals: Amer. J. Sci., 278A, 229 pp. 143.511 (Ref.: 78hel/del) Helgeson, H.C., Delany, J.M, Nesbitt, H.W., and Bird, D.K., 1978. Summary and Critique of the Thermodynamic Properties of Rock Forming Minerals: Amer. J. Sci., 278A, 229 pp. 76.12 (Ref.: 78hel/del) Helgeson, H.C., Delany, J.M, Nesbitt, H.W., and Bird, D.K., 1978. Summary and Critique of the Thermodynamic Properties of Rock Forming Minerals: Amer. J. Sci., 278A, 229 pp.
CP(T) = a + b·T + ·c·T-2 (T in Kelvin)
a
J·mol-1·K-1
 b * 103
J·mol-1·K-2
 c * 10-5
J·K·mol-1
 Maier Kelley Ref.
65.40 35.98 0.00 (Ref.: 78hel/del) Helgeson, H.C., Delany, J.M, Nesbitt, H.W., and Bird, D.K., 1978. Summary and Critique of the Thermodynamic Properties of Rock Forming Minerals: Amer. J. Sci., 278A, 229 pp.
Reaction properties

Acanthite(alpha) + H+ ⇌ 2Ag+ + HS-

298.15 K, 1 bar log10K: -36.07 ΔH°r:226837 J·mol-1 (Ref.: 78hel/del) Helgeson, H.C., Delany, J.M, Nesbitt, H.W., and Bird, D.K., 1978. Summary and Critique of the Thermodynamic Properties of Rock Forming Minerals: Amer. J. Sci., 278A, 229 pp.
T(°C) 0 25 60 100 150 200 250 300
log10K -39.73 -36.07 -31.92 -28.16 -24.50 -21.68 -19.50 -17.91
log10K(T) = A + B·T + C·T-1 + D·log10(T) + E·T−2 (T in Kelvin)
A B C D E
-886.682773 -0.132494 37956.106260 321.768750 -2967724.171183