Yanomamite is an extremely rare indium arsenate mineral found in specific hydrothermal environments. Collectors generally look for its distinctive yellow to yellow-green micro-crystalline crusts which appear in association with arsenopyrite deposits.
Is this yanomamite?
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 yanomamite with a known reference. Yanomamite sits at Mohs 2 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Yanomamite leaves a yellow streak.
- 3Read the lusterHold the specimen under a strong light. Yanomamite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: yellow, yellow-green.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: microcrystalline crusts, tiny tabular crystals.
Often confused with
Yanomamite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Scorodite is the harder of the two (Mohs 3.5-4 vs. 2); streak differs — Yanomamite leaves yellow, Scorodite leaves white; luster reads vitreous on Yanomamite and vitreous to sub-adamantine on Scorodite.
How to tell apart: Mansfieldite is the harder of the two (Mohs 3.5-4 vs. 2); streak differs — Yanomamite leaves yellow, Mansfieldite leaves white.
Often found alongside yanomamite
Minerals reported to co-occur with yanomamite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- InAsO₄·2H₂O
- Mohs hardness
- 2
- Density
- 3.32 g/cm³
- Colors
- Streak
- Yellow
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Microcrystalline Crusts, Tiny Tabular Crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Veins
- Typical price
- $50-300 per specimen
Where rockhounds find yanomamite
Classic worldwide localities
- Yanomami mine, Brazil
- Tsumeb mine, Namibia
Field-hunting tip
Look in hydrothermal veins country — that is the host setting where yanomamite typically forms. If you start seeing arsenopyrite, cassiterite in float, you are in the right ground. Field specimens usually show a microcrystalline crusts, tiny tabular crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find yanomamite on the map
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