Acanthite Mineral Data

Acanthite Mineral Data +

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General Acanthite Information

Chemical Formula:

Ag2S

Composition:

Molecular Weight = 247.80 gm

Silver 87.06 % Ag

Sulfur 12.94 % S

______

100.00 %

Empirical Formula:

Ag₂S

Environment:

Low-temperature sulfide veins and in zones of secondary enrichment.

IMA Status:

Valid Species (Pre-IMA) 1855

Locality:

Freiberg, Schneeberg, Annaberg, Germany. Link to MinDat.org Location Data.

Name Origin:

From the Greek, akanta, meaning "arrow." After the Latin, argentum, meaning "silver". Argentite is stable above 179 C. Acanthite is stable below 179 deg. C.

Synonym:

ICSD 30445

PDF 14-72

Silver Glance

Acanthite Image

Images:

Acanthite

Comments: Pseudo cubic acanthite crystals on matrix.
Location: Rayas mine, Guanajuato, Mexico. Scale: Size Not Given.
© Lou Perloff / Photo Atlas of Minerals

Images:

Acanthite Argentite

Comments: Dark metallic acanthite crystals up to 3 mm. Most of the crystals are a cubic habit, so the acanthite is pseudomorphing the original argentite.
Location: San Juan de Rayas Mine (Rayas Mine), Guanajuato, Mun. de Guanajuato, Guanajuato, Mexico. Scale: 18x12x12 mm.
© John Betts - Fine Minerals

Acanthite Crystallography

Axial Ratios:

a:b:c =0.6101:1:1.1343

Cell Dimensions:

a = 4.229, b = 6.931, c = 7.862, Z = 4; beta = 99.61° V = 227.21 Den(Calc)= 7.24

Crystal System:

Monoclinic - PrismaticH-M Symbol (2/m) Space Group: P 2₁/n

$Help on X Ray Diffraction:$ X Ray Diffraction:

By Intensity(I/I_o): 2.606(1), 2.44(0.8), 2.383(0.75),

Crystal Structure:

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drag2 - RMB Resize/Rotate
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Wiegers G A , American Mineralogist , 56 (1971) p.1882-1888, The crystal structure of the low-temperature form of silver selenide

Physical Properties of Acanthite

Cleavage:

[001] Poor, [110] Poor

Color:

Lead gray, Gray, Iron black.

Density:

7.2 - 7.4, Average = 7.3

Diaphaniety:

Opaque

Fracture:

Sectile - Curved shavings or scrapings produced by a knife blade, (e.g. graphite).

Habit:

Arborescent - "Tree like" growths of branched systems (e.g. silver).

Habit:

Blocky - Crystal shape tends to be equant (e.g. feldspars).

Habit:

Skeletal - Crystals form crude outlines with missing faces.

Hardness:

2-2.5 - Gypsum-Finger Nail

Luminescence:

None.

Luster:

Metallic

Magnetism:

Nonmagnetic

Streak:

shining black

Optical Properties of Acanthite

RL Anisotrophism:

Weak.

RL Bireflectance:

None.

RL Pleochroism:

None.

Reflectivity

**Standardized Intensity (100%) Reflection Spectra of Acanthite in Air**
λ	R	∑ R(λ)
420 nm	32.90
440 nm	33.00
460 nm	33.10
480 nm	33.00
500 nm	32.70
520 nm	32.00
540 nm	31.20
560 nm	30.50
580 nm	29.90
600 nm	29.20
620 nm	28.70
640 nm	28.20
660 nm	27.60
680 nm	27.00
700 nm	26.40

**Calculated Relative Intensity Colors of Acanthite in Air**
Relative Intensity	0%	40%	80%	100%	120%	160%	200%	240%	280%	310%
R

Calculated Properties of Acanthite

Electron Density:

r_electron=6.43 gm/cc
note: r_Acanthite=7.24 gm/cc.

Fermion Index

Fermion Index = 0.00097
Boson Index = 0.99903

Photoelectric:

PE_Acanthite= 224.26 barns/electron
U=PE_Acanthite x r_electron=1,441.48 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Acanthite is Not Radioactive

Acanthite Classification

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

2.4.1.1 Acanthite Ag2S P 2₁/n 2/m

2.4.1.2 Naumannite Ag2Se P 2₁2₁2₁ 2 2 2

2.4.1.3 Aguilarite Ag4SeS P 2₁2₁2₁ 2 2 2

Strunz Class:

II/B.05-10 II - Sulfides and sulphosalts

II/B - Sulfides with metal: sulfur, selenium and tellurium > 1:1, Sulfides, Selenides and Tellurides with predominant Copper and Silver/Gold

II/B.05 - Achantite - Empresite series

II/B.05-02 Argentite* Ag2S I m3m 4/m 3 2/m

II/B.05-10 Acanthite Ag2S P 2₁/n 2/m

II/B.05-30 Naumannite Ag2Se P 2₁2₁2₁ 2 2 2

II/B.05-35 Kurilite* (Ag,Au)2(Te,Se,S) P m3n,P 4₃n Cubic

II/B.05-40 Hessite Ag2Te P 2₁/c 2/m

II/B.05-50 Aguilarite Ag4SeS P 2₁2₁2₁ 2 2 2

II/B.05-60 Cervelleite Ag4TeS Unk Cubic

II/B.05-70 Benleonardite Ag8(Sb,As)Te2S3 Tetra Tetra

II/B.05-75 Tsnigriite Ag9SbTe3(S,Se)3 P 2/m,Pm Mono

II/B.05-80 Stutzite Ag5-xTe3,(x=0.24-0.36) P 6/mmm 6/m 2/m 2/m

II/B.05-90 Empressite AgTe Pmnb 2/m 2/m 2/m

Other Acanthite Information

References:

NAME( Duda&Rejl90) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(AntBidBlaNic1)

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Acanthite

Ag2S
Dana No: 2.4.1.1 Strunz No: II/B.05-10
Locality:

Notes: