Carobbiite is a rare potassium fluoride mineral typically found as small, colorless crystals in volcanic environments or pegmatites. It is highly water-soluble and can be easily confused with halite or sylvite, though it is usually distinguished by its specific formation environment and chemical tests.

Hardness

2-2.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Semitransparent

mineralrare

Carobbiite

Hardness: 2-2.5
Luster: Vitreous
Streak: White
Transparency: Semitransparent

Is this carobbiite?

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 carobbiite with a known reference. Carobbiite 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.
4
Match the color range
Compare against the expected color range: colorless.
5
Look at form & habit
Crystal system: cubic. Typical habit: octahedral, massive, granular.

Often confused with

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

Often found alongside carobbiite

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

All properties

Chemical formula: KF
Mohs hardness: 2-2.5
Density: 2.524 g/cm³
Colors: Colorless
Streak: White
Luster: Vitreous
Transparency: Semitransparent
Crystal system: Cubic
Crystal habit: Octahedral, massive, granular
Cleavage: {001}
Rarity: Rare
Uses: Collector
Host rock: In stalactites in cavities in lava

Where rockhounds find carobbiite

Classic worldwide localities

Vesuvius, Campania, Italy

Field-hunting tip

Where it forms: In stalactites in cavities in lava. If you start seeing halite, mercallite, hieratite in float, you are in the right ground. Typical habit: octahedral, massive, granular. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify carobbiite?+

Mohs hardness is 2-2.5. Luster: vitreous. The streak is white. Common colors include colorless.

Where is carobbiite found?+

Notable localities include Vesuvius, Campania, Italy.

Is carobbiite safe to handle?+

Carobbiite contains soluble fluoride and calls for real care. Contains fluorine and can be toxic if ingested or inhaled as dust; handle with care and wash hands thoroughly after contact.

What rocks look like carobbiite?+

Carobbiite is most often confused with Halite, Sylvite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with carobbiite?+

Carobbiite commonly co-occurs with Halite, Mercallite, Hieratite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does carobbiite form in?+

Where it forms: In stalactites in cavities in lava. Working float back to the host body is the standard way to chase a fresh occurrence.

What is carobbiite used for?+

Carobbiite is used in collector.

Find carobbiite on the map

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