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 1-2, 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: dull.
- 4Match the color rangeCompare against the expected color range: white.
- 5Look at form & habitCrystal system: triclinic. Typical habit: microscopic crystals, platy, pseudo rhombohedral.
Often confused with
Scarbroite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads dull on Scarbroite and pearly to dull earthy on Kaolinite.
How to tell apart: Allophane is the harder of the two (Mohs 3 vs. 1-2); luster reads dull on Scarbroite and vitreous to earthy, waxy on Allophane.
How to tell apart: Luster reads dull on Scarbroite and vitreous, pearly on cleavage surfaces, dull in aggregates 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
- 1-2
- Density
- 2.01 g/cm³
- Colors
- Streak
- White
- Luster
- Dull
- Transparency
- Semitransparent
- Crystal system
- Triclinic
- Crystal habit
- Microscopic crystals, platy, pseudo rhombohedral
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In vertical fissures in sandstone (Scarborough, England); authigenic, probably formed by dessication of near-shore bottom sediments of a hypersaline lake (Muskiki Lake, Canada)
Where rockhounds find scarbroite
Classic worldwide localities
- South Bay, near Scarborough, North Yorkshire, and at Weston Favell, Northampton, England
- Nikšić, Yugoslavia
- Muskiki Lake, Saskatchewan, Canada
Field-hunting tip
Where it forms: In vertical fissures in sandstone (Scarborough, England); authigenic, probably formed by dessication of near-shore bottom sediments of a hypersaline lake (Muskiki Lake, Canada). If you start seeing hydroscarbroite, gibbsite, kaolinite in float, you are in the right ground. Typical habit: microscopic crystals, platy, pseudo rhombohedral. 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?+
What kind of rock does scarbroite form in?+
What is scarbroite used for?+
Find scarbroite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
