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 2-2.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: colorless.
- 5Look at form & habitCrystal system: triclinic. Typical habit: spherical, tabular.
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
- 2-2.5
- Density
- 1.85 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Triclinic
- Crystal habit
- Spherical, tabular
- Cleavage
- On {010}, good
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In veinlets cutting metamorphosed Mn–Ba-rich cherts in an obducted ophiolite
Where rockhounds find caoxite
Classic worldwide localities
- Cerchiara mine, near Faggiona, Val di Vara, Liguria, Italy
Field-hunting tip
Where it forms: In veinlets cutting metamorphosed Mn–Ba-rich cherts in an obducted ophiolite. If you start seeing quartz, barite, manganese oxides in float, you are in the right ground. Typical habit: spherical, tabular. Train your eye for that shape before scanning the outcrop.
Common questions
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Find caoxite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
