Clairite is a very rare ammonium-bearing sulfate mineral often found in the oxidized zones of coal mine dumps. It typically appears as small, yellowish, pearly tabular crystals and is distinguished from common copiapite by its ammonium content and specific geological setting.
Is this clairite?
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 clairite with a known reference. Clairite 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. Streak: yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: pearly.
- 4Match the color rangeCompare against the expected color range: yellow.
- 5Look at form & habitCrystal system: triclinic. Typical habit: tabular crystals.
Often confused with
Clairite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside clairite
Minerals reported to co-occur with clairite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (NH₄)₂Fe₃(SO₄)₄(OH)₃·3H₂O
- Mohs hardness
- 2
- Density
- 2.31 g/cm³
- Colors
- Streak
- Yellow
- Luster
- Pearly
- Transparency
- Transparent to translucent
- Crystal system
- Triclinic
- Crystal habit
- Tabular crystals
- Cleavage
- Perfect on {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A rare secondary mineral formed by alteration of pyrite to ferric sulfate, and reaction, at pH ∼2, with ammonia produced as the result of decay of organic matter (Hyrax excreta)
Where rockhounds find clairite
Classic worldwide localities
- Lone Creek Fall cave, near Sbri, eastern Transvaal, South Africa (type locality)
Field-hunting tip
Where it forms: A rare secondary mineral formed by alteration of pyrite to ferric sulfate, and reaction, at pH ∼2, with ammonia produced as the result of decay of organic matter (Hyrax excreta). If you start seeing lonecreekite, sabieite, tschermigite in float, you are in the right ground. Typical habit: tabular crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify clairite?+
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What rocks look like clairite?+
What minerals are found with clairite?+
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Find clairite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
