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: triclinic. 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
- Translucent
- Crystal system
- Triclinic
- Crystal habit
- Massive, Chalky, Or Botryoidal Crusts
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Sedimentary Ironstone or Clay Beds
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, 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
How do you identify scarbroite?+
Where is scarbroite found?+
What rocks look like scarbroite?+
What minerals are found with scarbroite?+
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Find scarbroite on the map
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