Caoxite is a rare calcium oxalate mineral typically found in association with organic-rich coal environments. It usually occurs as small, delicate yellowish crystals that are highly prized by collectors of rare minerals.
Is this caoxite?
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 caoxite with a known reference. Caoxite 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. Caoxite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Caoxite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: yellow, yellowish-brown.
- 5Look at form & habitCrystal system: triclinic. Typical habit: tabular crystals.
Often confused with
Caoxite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside caoxite
Minerals reported to co-occur with caoxite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca(C₂O₄)·3H₂O
- Mohs hardness
- 2
- Density
- 2.44 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Triclinic
- Crystal habit
- Tabular Crystals
- Cleavage
- Perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Coal Seams
- Typical price
- $50-300 per specimen
Where rockhounds find caoxite
Classic worldwide localities
- Cegelska, Slovakia
- Most, Czech Republic
Field-hunting tip
Look in coal seams country — that is the host setting where caoxite typically forms. If you start seeing whewellite, weddellite in float, you are in the right ground. Field specimens usually show a tabular crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find caoxite on the map
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