Caresite is a rare iron aluminum carbonate that forms green-black tabular crystals. It is a late-stage hydrothermal mineral in an alkaline complex. It was first described from Poudrette quarry, Monteregian Hills, Quebec, Canada.
Is this caresite?
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 caresite with a known reference. Caresite 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: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: colorless, yellow, orange brown.
- 5Look at form & habitCrystal system: trigonal. Typical habit: prismatic, tabular.
Often confused with
Caresite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads vitreous on Caresite and subvitreous, pearly on {010} cleavages, silky if fibrous on Gypsum.
How to tell apart: Anhydrite is the harder of the two (Mohs 3-3.5 vs. ~2); luster reads vitreous on Caresite and pearly on {010}, vitreous to greasy on {001}; vitreous on {100} on Anhydrite.
Often found alongside caresite
Minerals reported to co-occur with caresite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Fe²⁺₄Al₂(OH)₁₂(CO₃)·3H₂O
- Mohs hardness
- ~2
- Density
- 2.59 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Trigonal
- Crystal habit
- Prismatic, tabular
- Cleavage
- Perfect on {0001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A late-stage hydrothermal mineral in an alkaline complex
Where rockhounds find caresite
Classic worldwide localities
- Poudrette quarry, Mont Saint-Hilaire, and the old Corporation quarry, Mont Royal, Montreal, Monteregian Hills, Quebec, Canada
Field-hunting tip
Where it forms: A late-stage hydrothermal mineral in an alkaline complex. If you start seeing microcline, analcime, natrolite in float, you are in the right ground. Typical habit: prismatic, tabular. Train your eye for that shape before scanning the outcrop.
Common questions
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Find caresite on the map
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