Kumtyubeite is a very rare calcium silicate fluoride mineral discovered in the pyrometamorphic rocks of the Northern Caucasus. It typically forms small tabular crystals within high-temperature combustion metamorphic assemblages and is highly prized by advanced mineral collectors.

Hardness

5-6

Mohs

Luster

Vitreous

Transparency

Transparent

mineralrareHatrurite Group family

Kumtyubeite

Hardness: 5-6
Luster: Vitreous
Transparency: Transparent

Is this kumtyubeite?

4-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 kumtyubeite with a known reference. Kumtyubeite sits at Mohs 5-6, softer than the next harder reference, harder than the previous one.
2
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
3
Match the color range
Compare against the expected color range: light-pink, colorless.
4
Look at form & habit
Crystal system: monoclinic. Typical habit: tabular crystals.

Often confused with

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

Often found alongside kumtyubeite

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

All properties

Chemical formula: Ca₅(SiO₄)₂F₂
Mohs hardness: 5-6
Density: 2.866 g/cm³
Colors: Light-pink Colorless
Luster: Vitreous
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Tabular crystals
Cleavage: Distinct on (001), particularly for OH:F ≈ 1
Rarity: Rare
Uses: Collector
Host rock: A rock-forming mineral in contact-metasomatic, spurrite-rondorfite-ellestadite skarn in carbonate-xenoliths in ignimbrites

Where rockhounds find kumtyubeite

Classic worldwide localities

Kabardino-Balkaria, North Caucasus, Russia (type locality)

Field-hunting tip

Where it forms: A rock-forming mineral in contact-metasomatic, spurrite-rondorfite-ellestadite skarn in carbonate-xenoliths in ignimbrites. If you start seeing rondorfite, lakargiite, kimzeyite in float, you are in the right ground. Typical habit: tabular crystals. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify kumtyubeite?+

Mohs hardness is 5-6. Luster: vitreous. Common colors include light-pink, colorless.

Where is kumtyubeite found?+

Notable localities include Kabardino-Balkaria, North Caucasus, Russia (type locality).

What rocks look like kumtyubeite?+

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

What minerals are found with kumtyubeite?+

Kumtyubeite commonly co-occurs with Rondorfite, Lakargiite, Kimzeyite, Srebrodolskite, Bultfonteinite, Ca-hydrosilicates. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does kumtyubeite form in?+

Where it forms: A rock-forming mineral in contact-metasomatic, spurrite-rondorfite-ellestadite skarn in carbonate-xenoliths in ignimbrites. Working float back to the host body is the standard way to chase a fresh occurrence.

What is kumtyubeite used for?+

Kumtyubeite is used in collector.

Find kumtyubeite on the map

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