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

3.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrareHatrurite Group family

Kumtyubeite

Hardness: 3.5
Luster: Vitreous
Streak: White
Transparency: Transparent

Is this kumtyubeite?

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 kumtyubeite with a known reference. Kumtyubeite sits at Mohs 3.5 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Kumtyubeite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Kumtyubeite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: white, colorless.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: tabular crystals.

Often confused with

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

How to tell apart: Rankinite is the harder of the two (Mohs 5.5 vs. 3.5).

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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: Ca₄(Si₂O₇)F₂
Mohs hardness: 3.5
Density: 3.17 g/cm³
Colors: White Colorless
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Orthorhombic
Crystal habit: Tabular Crystals
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Pyrometamorphic Rocks
Typical price: $50-300 per specimen

Where rockhounds find kumtyubeite

Classic worldwide localities

Kumtyube, Kabardino-Balkarian Republic, Russia

Field-hunting tip

Look in pyrometamorphic rocks country — that is the host setting where kumtyubeite typically forms. If you start seeing ettringite, portlandite, afwillite in float, you are in the right ground. Field specimens usually show a tabular crystals habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify kumtyubeite?+

Mohs hardness is 3.5. It typically shows a vitreous luster. The streak is white. Common colors include white, colorless.

Where is kumtyubeite found?+

Notable localities include Kumtyube, Kabardino-Balkarian Republic, Russia.

How much is kumtyubeite worth?+

Typical asking prices fall in the range of $50-300 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

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 Ettringite, Portlandite, Afwillite, Calcite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does kumtyubeite form in?+

Kumtyubeite typically forms in pyrometamorphic rocks. 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.