Hydroscarbroite is a rare aluminum carbonate mineral typically found as white, chalky, or botryoidal coatings within clay-rich sedimentary environments. It is most easily identified by its soft, porcelain-like appearance and its association with other aluminum-rich secondary minerals in coastal cliff settings.

Hardness

2-3

Mohs

Luster

Dull

Streak

White

Transparency

Opaque

mineralrareScarbroite family

Hydroscarbroite

Hardness: 2-3
Luster: Dull
Streak: White
Transparency: Opaque

Is this hydroscarbroite?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch hydroscarbroite with a known reference. Hydroscarbroite sits at Mohs 2-3 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Hydroscarbroite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Hydroscarbroite typically shows a dull luster.
4
Match the color range
Compare against the expected color range: white.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: massive, chalky, or botryoidal crusts.

Often confused with

Hydroscarbroite vs. its common look-alikes — and how to tell them apart in the field.

How to tell apart: Luster reads dull on Hydroscarbroite and vitreous on Gibbsite.

Often found alongside hydroscarbroite

Minerals reported to co-occur with hydroscarbroite. 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)₃₆·n H₂O
Mohs hardness: 2-3
Density: 2.1-2.2 g/cm³
Colors: White
Streak: White
Luster: Dull
Transparency: Opaque
Crystal system: Orthorhombic
Crystal habit: Massive, Chalky, Or Botryoidal Crusts
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Sedimentary Clay Beds and Fissures in Sandstone
Typical price: $20-100 per specimen

Where rockhounds find hydroscarbroite

Classic worldwide localities

Scarborough, North Yorkshire, England
Various clay-rich sedimentary deposits

Field-hunting tip

Look in sedimentary clay beds and fissures in sandstone country — that is the host setting where hydroscarbroite typically forms. If you start seeing kaolinite, gibbsite, allophane 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 hydroscarbroite?+

Mohs hardness is 2-3. It typically shows a dull luster. The streak is white. Common colors include white.

Where is hydroscarbroite found?+

Notable localities include Scarborough, North Yorkshire, England; Various clay-rich sedimentary deposits.

How much is hydroscarbroite worth?+

Typical asking prices fall in the range of $20-100 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like hydroscarbroite?+

Hydroscarbroite is most often confused with Scarbroite, Gibbsite, Kaolinite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with hydroscarbroite?+

Hydroscarbroite commonly co-occurs with Kaolinite, Gibbsite, Allophane. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does hydroscarbroite form in?+

Hydroscarbroite typically forms in sedimentary clay beds and fissures in sandstone. Working float back to the host body is the standard way to chase a fresh occurrence.

What is hydroscarbroite used for?+

Hydroscarbroite is used in collector.

Find hydroscarbroite on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.