Sergeevite is a rare hydrated calcium magnesium carbonate mineral typically found in sedimentary evaporite environments. It usually appears as fine-grained, pearly white crusts or platy aggregates, making it difficult to distinguish from common carbonates without chemical testing.
Is this sergeevite?
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 sergeevite with a known reference. Sergeevite sits at Mohs ~3.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: dull.
- 4Match the color rangeCompare against the expected color range: white.
- 5Look at form & habitCrystal system: trigonal. Typical habit: aggregates.
Often confused with
Sergeevite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads dull on Sergeevite and vitreous; pearly on cleavages and {0001} on Calcite.
How to tell apart: Luster reads dull on Sergeevite and vitreous to pearly on Dolomite.
How to tell apart: Luster reads dull on Sergeevite and vitreous; silky to pearly to dull in aggregates on Hydromagnesite.
Often found alongside sergeevite
Minerals reported to co-occur with sergeevite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₂Mg₁₁(CO₃)₉(HCO₃)₄(OH)₄·6H₂O
- Mohs hardness
- ~3.5
- Density
- 2.55-2.87 g/cm³
- Colors
- Streak
- White
- Luster
- Dull
- Transparency
- Semitransparent
- Crystal system
- Trigonal
- Crystal habit
- Aggregates
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A weathering product of pyroxene–garnet skarn
Where rockhounds find sergeevite
Classic worldwide localities
- Malyi Mukulan tin deposit, Tyrnyauz district, Baksan River Valley, northern Caucasus Mountains, Russia
Field-hunting tip
Where it forms: A weathering product of pyroxene–garnet skarn. If you start seeing huntite, chrysocolla, chalcanthite in float, you are in the right ground. Typical habit: aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify sergeevite?+
Where is sergeevite found?+
What rocks look like sergeevite?+
What minerals are found with sergeevite?+
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Find sergeevite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
