Efremovite is a rare sulfate mineral that typically forms as a result of spontaneous combustion in coal mine dumps. It is structurally part of the langbeinite group and is primarily found as small, yellowish or colorless crystals associated with other minerals formed by fumarolic or pyrometamorphic processes in burning coal seams.
Is this efremovite?
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 efremovite with a known reference. Efremovite sits at Mohs ~2, 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: vitreous.
- 4Match the color rangeCompare against the expected color range: gray white, white.
- 5Look at form & habitCrystal system: cubic. Typical habit: equant crystals, granular.
Often confused with
Efremovite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside efremovite
Minerals reported to co-occur with efremovite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (NH₄)₂Mg₂(SO₄)₃
- Mohs hardness
- ~2
- Density
- 2.52 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent to nearly opaque
- Crystal system
- Cubic
- Crystal habit
- Equant crystals, granular
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- As crusts on burning coal mine dumps, formed by the reaction of combustion gases with carbonate rocks
Where rockhounds find efremovite
Classic worldwide localities
- Kopeysk, in the Chelyabinsk coal basin, Southern Ural Mountains, Russia
- Scholler mine, near Kladno, Czech Republic
Field-hunting tip
Where it forms: As crusts on burning coal mine dumps, formed by the reaction of combustion gases with carbonate rocks. If you start seeing sulfur, kladnoite, mascagnite in float, you are in the right ground. Typical habit: equant crystals, granular. Train your eye for that shape before scanning the outcrop.
Common questions
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Find efremovite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
