Kochsándorite is a very rare hydrated magnesium aluminum carbonate mineral typically found in sedimentary deposits. It usually appears as white, earthy, or microcrystalline crusts and is challenging to distinguish from other similar white powdery minerals without chemical analysis.

Hardness

2-2.5

Mohs

Luster

Vitreous, silky in aggregates

Streak

White

Transparency

Transparent

mineralrareAluminite Group family

Kochsándorite

Hardness: 2-2.5
Luster: Vitreous, silky in aggregates
Streak: White
Transparency: Transparent

Is this kochsándorite?

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 kochsándorite with a known reference. Kochsándorite sits at Mohs 2-2.5, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: white.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous, silky in aggregates.
4
Match the color range
Compare against the expected color range: white.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: acicular, radial.

Often confused with

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

mineral

Aluminite

Mohs 1-2

How to tell apart: Luster reads vitreous, silky in aggregates on Kochsándorite and dull to earthy on Aluminite.

Compare →

Often found alongside kochsándorite

Minerals reported to co-occur with kochsándorite. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: CaAl₂(CO₃)₂(OH)₄·H₂O
Mohs hardness: 2-2.5
Density: 2.486 g/cm³
Colors: White
Streak: White
Luster: Vitreous, silky in aggregates
Transparency: Transparent
Crystal system: Orthorhombic
Crystal habit: Acicular, radial
Cleavage: None
Fluorescence: Fluoresces pale yellow under SW and LW UV
Rarity: Rare
Uses: Collector
Host rock: A secondary mineral formed by the contemporaneous weathering of böhmite, pyrite and calcite in brown coal beds

Where rockhounds find kochsándorite

Classic worldwide localities

Hungary
Czech Republic

Field-hunting tip

Where it forms: A secondary mineral formed by the contemporaneous weathering of böhmite, pyrite and calcite in brown coal beds. If you start seeing quartz, pyrite, böhmite in float, you are in the right ground. Typical habit: acicular, radial. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify kochsándorite?+

Mohs hardness is 2-2.5. Luster: vitreous, silky in aggregates. The streak is white. Common colors include white.

Where is kochsándorite found?+

Notable localities include Hungary; Czech Republic.

What rocks look like kochsándorite?+

Kochsándorite is most often confused with Aluminite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with kochsándorite?+

Kochsándorite commonly co-occurs with Quartz, Pyrite, Böhmite, Dolomite, Calcite, Gibbsite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does kochsándorite form in?+

Where it forms: A secondary mineral formed by the contemporaneous weathering of böhmite, pyrite and calcite in brown coal beds. Working float back to the host body is the standard way to chase a fresh occurrence.

What is kochsándorite used for?+

Kochsándorite is used in collector.

Find kochsándorite on the map

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