Scarbroite is a very rare aluminum carbonate mineral that typically occurs as soft, white, chalky masses or thin crusts. It is most famous for its occurrence in the iron-rich sedimentary deposits near Scarborough, England, where it was first discovered.
Is this scarbroite?
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 scarbroite with a known reference. Scarbroite 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. Scarbroite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Scarbroite typically shows a dull luster.
- 4Match the color rangeCompare against the expected color range: white, creamy white.
- 5Look at form & habitCrystal system: amorphous. Typical habit: massive, chalky, or botryoidal crusts.
Often confused with
Scarbroite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Allophane is the harder of the two (Mohs 3 vs. 2); luster reads dull on Scarbroite and vitreous on Allophane.
How to tell apart: Luster reads dull on Scarbroite and vitreous on Gibbsite.
Often found alongside scarbroite
Minerals reported to co-occur with scarbroite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Al₁₄(CO₃)₃(OH)₃₀·nH₂O
- Mohs hardness
- 2
- Density
- 2.1-2.2 g/cm³
- Colors
- Streak
- White
- Luster
- Dull
- Transparency
- Opaque
- Crystal system
- Amorphous
- Crystal habit
- Massive, Chalky, Or Botryoidal Crusts
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Sedimentary Ironstone or Clay Beds
- Typical price
- $20-100 per specimen
Where rockhounds find scarbroite
Classic worldwide localities
- Scarborough, North Yorkshire, England
- Cornwall, England
- Thuringia, Germany
Field-hunting tip
Look in sedimentary ironstone or clay beds country — that is the host setting where scarbroite typically forms. If you start seeing calcite, goethite, quartz in float, you are in the right ground. Field specimens usually show a massive, chalky, or botryoidal crusts habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find scarbroite on the map
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