Aramayoite is a rare silver-antimony sulfosalt known primarily from its type locality in the silver-tin mines of Bolivia. It typically occurs as opaque, black to metallic gray tabular crystals and is highly prized by mineral collectors specializing in rare sulfosalts.
Is this aramayoite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch aramayoite with a known reference. Aramayoite sits at Mohs 2.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: black to red-brown.
- 3Read the lusterHold the specimen under a strong light. Luster: brilliant metallic.
- 4Match the color rangeCompare against the expected color range: iron black, deep blood red.
- 5Look at form & habitCrystal system: triclinic. Typical habit: pseudo tetragonal.
Often confused with
Aramayoite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Aramayoite leaves black to red-brown, Miargyrite leaves cherry-red; luster reads brilliant metallic on Aramayoite and metallic adamantine on Miargyrite.
How to tell apart: Streak differs, so Aramayoite leaves black to red-brown, Matildite leaves pale gray; luster reads brilliant metallic on Aramayoite and metallic on Matildite.
Often found alongside aramayoite
Minerals reported to co-occur with aramayoite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ag₃(Sb,Bi)₂S₄
- Mohs hardness
- 2.5
- Density
- 5.602 g/cm³
- Colors
- Iron blackDeep blood red
- Streak
- Black to red-brown
- Luster
- Brilliant metallic
- Transparency
- Opaque
- Crystal system
- Triclinic
- Crystal habit
- Pseudo tetragonal
- Cleavage
- Perfect on {010}, fair on {100}, poor on {001}
- Rarity
- Rare
- Uses
- Collector, Scientific research
- Host rock
- Rare, typically in vein-controlled hydrothermal Sn–Ag ores
Where rockhounds find aramayoite
Classic worldwide localities
- Flathead mine, about 13 km north of Niarada, Flathead Co., Montana, USA
- Animas mine, Chocaya, Potosí, Bolivia (type locality)
- Herminia, Julcani district, and in the San Genaro mine, Huancavelica, Peru
- Armonia mine, El Quevar, Salta Province, and in the Pirquitas deposit, Riconada Department, Jujuy Province, Argentina
- Portugalete, Bolivia
- El Indio mine, El Indio-Tambo district, east of La Serena, Coquimbo, Chile
Field-hunting tip
Where it forms: Rare, typically in vein-controlled hydrothermal Sn–Ag ores. If you start seeing tetrahedrite, miargyrite, stannite in float, you are in the right ground. Typical habit: pseudo tetragonal. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify aramayoite?+
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What rocks look like aramayoite?+
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Find aramayoite on the map
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