Rustumite is a rare calcium silicate chloride mineral typically found in high-temperature metamorphic environments such as spurrite skarns. It often appears as colorless to white tabular crystals or massive aggregates within complex mineral assemblages. It was first identified in the Chegem caldera and is highly sought after by systematic mineral collectors.
Is this rustumite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch rustumite with a known reference. Rustumite sits at Mohs 4-5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Rustumite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Rustumite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: colorless, white, pale yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular crystals, massive, granular.
Often confused with
Rustumite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside rustumite
Minerals reported to co-occur with rustumite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₁₀(Si₂O₇)₂Cl₂(OH)₂
- Mohs hardness
- 4-5
- Density
- 2.99 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular Crystals, Massive, Granular
- Cleavage
- Good
- Rarity
- Rare
- Uses
- Collector, Scientific Research
- Host rock
- Skarn and High-temperature Metamorphic Rocks
- Typical price
- n/a
Where rockhounds find rustumite
Classic worldwide localities
- Chegem caldera, Kabardino-Balkaria, Russia
- Hatrurim Formation, Israel
- Negev Desert, Israel
Field-hunting tip
Look in skarn and high-temperature metamorphic rocks country — that is the host setting where rustumite typically forms. If you start seeing spurrite, ettringite, larnite in float, you are in the right ground. Field specimens usually show a tabular crystals, massive, granular habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find rustumite on the map
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