Mineral Information and Data:

Aramayoite
Ag3Sb2(Bi,Sb)S6 [CNMNC approved formula]

Named for Felix Avelino Aramayo, former Managing Director of the Compagnie Aramayo de Mines en Bolivie.

IMA status : Valid species (Pre-IMA 1926) Grandfathered
CLASSIFICATION 
Dana
(8th edition) :
03.07.04.01  
  (03) Sulfides - Sulfosalts
  (03.07) where z/y = 2 - (A+)i (A++)j [By Cz], A=metals, B=semi-metals, C=non-metals
  (03.07.04)
  
Nickel-Strunz
(10th edition) :
02.HA.25
  (02) Sulfides
  (02.H) Sulfosalts of SnS Archetype
  (02.HA) With Cu, Ag, Fe (without Pb)
  
Crystal system: Triclinic System
Point group (H-M): 1 — pinacoidal
Unit cell: a = 7.74Å, b = 8.84Å, c = 8.32Å α = 100.7°, β = 90°, γ = 103.9°
Crystal Habit: Aggregates thin broad plates parallel to (010), striated along {100} and {001}
Twinning: about [101] with the composition plane near {101}
  
Color: Iron-black
Diaphaneity: Nearly opaque
Luster: Metallic
Hardness (Mohs): 2.5
Measured Density: 5.60 g/cm3
Cleavage: 3; {010} perfect, {100} fair, {001} poor
Tenacity: Sectile, thin flakes are flexible but not elastic.
Streak: Black to red-brown
  
Geologic Setting: Rare, typically in vein-controlled hydrothermal Sn–Ag ores.
Mineral Association: Tetrahedrite, miargyrite, stannite, pyrite, quartz
  

 

Aramayoite
Aramayoite is present as large thin plates (blue iridescence) to 1mm in photo. Miargyrite is present as equant, blocky crystals to 1mm.
Origin: Julcani Silver mine, Huancavelica Dept., Peru
Sample size: 2.5 x 1.5 x 1.5 cm
Photo: Tom Loomis

 

Aramayoite
(zoom-in of above)

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