Combeite is an extremely rare silicate mineral found in alkaline volcanic environments. It is best known from the unique lavas of Mount Nyiragongo and Oldoinyo Lengai, where it occurs in small, colorless to pale yellow grains associated with nepheline and melilite.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrare

Combeite

Hardness: 5
Luster: Vitreous
Streak: White
Transparency: Transparent

Is this combeite?

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

Often confused with

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

How to tell apart: Luster reads vitreous on Combeite and vitreous to silky on Pectolite.

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Often found alongside combeite

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

All properties

Chemical formula: Na₂Ca₄Si₃O₉
Mohs hardness: 5
Density: 2.85 g/cm³
Colors: Colorless White Pale Yellow
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Trigonal
Crystal habit: Granular to Prismatic Crystals
Cleavage: Poor
Rarity: Rare
Uses: Collector
Host rock: Alkaline Volcanic Rocks
Typical price: $50-300 per specimen

Where rockhounds find combeite

Classic worldwide localities

Mount Nyiragongo, Democratic Republic of the Congo
Oldoinyo Lengai, Tanzania

Field-hunting tip

Look in alkaline volcanic rocks country — that is the host setting where combeite typically forms. If you start seeing nepheline, melilite, kalsilite in float, you are in the right ground. Field specimens usually show a granular to prismatic crystals habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify combeite?+

Mohs hardness is 5. It typically shows a vitreous luster. The streak is white. Common colors include colorless, white, pale yellow.

Where is combeite found?+

Notable localities include Mount Nyiragongo, Democratic Republic of the Congo; Oldoinyo Lengai, Tanzania.

How much is combeite 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 combeite?+

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

What minerals are found with combeite?+

Combeite commonly co-occurs with Nepheline, Melilite, Kalsilite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does combeite form in?+

Combeite typically forms in alkaline volcanic rocks. Working float back to the host body is the standard way to chase a fresh occurrence.

What is combeite used for?+

Combeite is used in collector.

Find combeite on the map

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