Agmantinite is a rare silver arsenic sulfide that occurs primarily as massive aggregates within silver-rich hydrothermal vein systems. It is physically similar to other silver sulfosalts and is typically identified through its metallic luster, black streak, and association with other silver-bearing minerals.
Is this agmantinite?
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 agmantinite with a known reference. Agmantinite sits at Mohs 2.5-3 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Agmantinite leaves a black streak.
- 3Read the lusterHold the specimen under a strong light. Agmantinite typically shows a metallic luster.
- 4Match the color rangeCompare against the expected color range: dark gray, black.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: massive, granular, or anhedral grains.
Often confused with
Agmantinite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Agmantinite leaves black, Proustite leaves scarlet; luster reads metallic on Agmantinite and adamantine on Proustite.
How to tell apart: Streak differs — Agmantinite leaves black, Pyrargyrite leaves red; luster reads metallic on Agmantinite and metallic to adamantine on Pyrargyrite.
Often found alongside agmantinite
Minerals reported to co-occur with agmantinite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ag₂AsS₃
- Mohs hardness
- 2.5-3
- Density
- 5.6-5.8 g/cm³
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Massive, Granular, Or Anhedral Grains
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Epithermal Silver-bearing Hydrothermal Veins
- Typical price
- $50-500 thumbnail
Where rockhounds find agmantinite
Classic worldwide localities
- Agua Blanca, Spain
- Chañarcillo, Chile
- Freiberg, Germany
Field-hunting tip
Look in epithermal silver-bearing hydrothermal veins country — that is the host setting where agmantinite typically forms. If you start seeing proustite, silver, galena in float, you are in the right ground. Field specimens usually show a massive, granular, or anhedral grains habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find agmantinite on the map
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