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Miargyrite

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Formula:
AgSbS2
System:
Monoclinic
Colour:
Black with dark red ...
Lustre:
Metallic
Hardness:
Name:
From Greek "meion" (less) and "argyros" (silver), for it contains less silver than pyrargyrite which it was often mistaken for.
The monoclinic dimorph of Cuboargyrite and Baumstarkite.

The Se analogue is known as 'UM1987-15-Se:AgSSb'.

Black blocky, often striated crystals with dark red internal reflections to a cm. The crystals are difficult to orient and often form balls to a few cm.

According to Nekrasov & Lunin (1987), the Se-free miargyrite (monoclinic, alpha form) transforms to the cubic (beta) form at 380°C, while the one containing 6.9 wt.% Se - at 300°C.


Classification of Miargyrite

Approved, 'Grandfathered' (first described prior to 1959)
2.HA.10

2 : SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulfantimonites, sulfbismuthites, etc.)
H : Sulfosalts of SnS archetype
A : With Cu, Ag, Fe (without Pb)
3.7.3.2

3 : SULFOSALTS
7 : ø = 2
5.2.8

5 : Sulphosalts - Sulpharsenites and Sulphobismuthites (those containing Sn, Ge,or V are in Section 6)
2 : Sulpharsenites etc. of Ag

Physical Properties of Miargyrite

Metallic
Colour:
Black with dark red internal reflections
Streak:
Cherry red
Hardness (Mohs):
Hardness Data:
Measured
Cleavage:
Imperfect/Fair
Imperfect on 010, rare on 100 and 101
Fracture:
Sub-Conchoidal
Density:
5.25 g/cm3 (Measured)    5.29 g/cm3 (Calculated)

Optical Data of Miargyrite

Type:
Biaxial (+)
RI values:
nα = 2.720 - 2.800
Max Birefringence:
δ = 2.720
Image shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:
Moderate
Dispersion:
relatively strong
Internal Reflections:
dark red internal reflections

Chemical Properties of Miargyrite

Formula:
AgSbS2
Elements listed in formula:
Common Impurities:
As,Fe

Crystallography of Miargyrite

Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
B2/b
Space Group Setting:
C2/c
Cell Parameters:
a = 12.862(3) Å, b = 4.409(1) Å, c = 13.218(3) Å
β = 98.48(2)°
Ratio:
a:b:c = 2.917 : 1 : 2.998
Unit Cell Volume:
V 741.38 ų (Calculated from Unit Cell)
Z:
8
Morphology:
Black, blocky, often striated crystals.
Comment:
Space group C2/c according to reinvestigation of Effenberger et al. (2002); space group was previously assumed to be either C2 (Smith et al., 1997) or Cc (Knowles, 1964). Unit-cell parameters also given as: 12.824(1), 4.4060(3), 13.193(1) Å, 98.567(6)° (Smith et al., 1997).

Crystallographic forms of Miargyrite

Crystal Atlas:
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Miargyrite - {100}, {010}, {001}, modified
Miargyrite - equant crystal
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Type Occurrence of Miargyrite

Empirical Formula:
AgSbS2

Relationship of Miargyrite to other Species

2.HA.05ChalcostibiteCuSbS2
2.HA.05EmplectiteCuBiS2
2.HA.20BerthieriteFeSb2S4
2.HA.20GaravelliteFeSbBiS4
2.HA.20CleriteMnSb2S4
2.HA.25AramayoiteAg3Sb2(Bi,Sb)S6
2.HA.25BaumstarkiteAg3Sb3S6
5.2.1SmithiteAgAsS2
5.2.2TrechmanniteAgAsS2
5.2.3ProustiteAg3AsS3
5.2.4XanthoconiteAg3AsS3
5.2.5Pearceite[Ag9CuS4][(Ag,Cu)6(As,Sb)2S7]
5.2.6Pearceite-T2ac
5.2.7ArgentotennantiteAg6[Cu4(Fe,Zn)2]As4S13
5.2.9PyrargyriteAg3SbS3
5.2.10PyrostilpniteAg3SbS3
5.2.11StephaniteAg5SbS4
5.2.12Polybasite[(Ag,Cu)6(Sb,As)2S7][Ag9CuS4]
5.2.13BillingsleyiteAg7AsS6
5.2.14Polybasite-Tac
5.2.15FreibergiteAg6[Cu4Fe2]Sb4S13-x
5.2.16AramayoiteAg3Sb2(Bi,Sb)S6
5.2.17MatilditeAgBiS2
5.2.18SchapbachiteAg0.4Pb0.2Bi0.4S
5.2.19PavoniteAgBi3S5
5.2.20ArcubisiteAg6CuBiS4
5.2.21BohdanowicziteAgBiSe2
5.2.22SelenostephaniteAg5Sb(Se,S)4
5.2.23Benleonardite[Ag6(Sb,As)2S6Te] [Ag9Cu(S,Te)2Te2]
5.2.24VolynskiteAgBiTe2

Other Names for Miargyrite

Other Information

Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Miargyrite

Reference List:
Hausmann (1805) Hercyn. Archiv: 4: 680.

Mohs, F. (1824) Hemiprismatische Rubinblende.- Grundriss der Mineralogie, vol. II, p. 606-607.

Rose, H. (1829) Ueber die in der Natur vorkommenden nicht oxydirten Verbindungen des Antimons und des Arseniks.- Poggendorffs Annalen der Physik und Chemie 15, 451-476.

Palache, Charles, Harry Berman & Clifford Frondel (1944) The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana Yale University 1837-1892, Volume I: Elements, Sulfides, Sulfosalts, Oxides. John Wiley and Sons, Inc., New York. 7th edition, revised and enlarged: 424-427.

Knowles, C.R. (1964): A redetermination of the structure of miargyrite, AgSbS2. Acta Crystallographica, 17, 847-851. [incorrectly cited as Knowles (1959) in Smith et al. (1997)]

Nekrasov, I. Ya., Lunin, S. Ye. (1987) Formation conditions of silver sulfides. selenides, and sulfoselenides in the system Ag-Sb-S-Se, determined experimentally. Mineral. Zhurnal: 9 (l): 25-39 (in Russian); in: Jambor, J.L., Vanko, D.A. (1989) New mineral Names. American Mineralogist: 74: 950.

Smith, J.V., Pluth, J.J., Han, S. (1997): Crystal structure refinement of miargyrite AgSbS2. Mineralogical Magazine, 61, 671-675.

Effenberger, H., Paar, W.H., Topa, D., Criddle, A.J., and Fleck, M. (2002): The new mineral baumstarkite and a structural reinvestigation of aramayoite and miargyrite. American Mineralogist 87, 753-764.

Internet Links for Miargyrite

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Specimens:
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Localities for Miargyrite

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