Rostite is a rare aluminum sulfate-fluoride hydrate that frequently forms as efflorescences or delicate crystal sprays on coal mine waste heaps. Because it is highly soluble and fragile, specimens should be stored in dry, airtight containers to prevent dehydration and crumbling. It is primarily sought by advanced mineral collectors specializing in secondary sulfate minerals.
Is this rostite?
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 rostite with a known reference. Rostite 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. Rostite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Rostite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, colorless, yellow.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: prismatic crystals, coatings, crusts.
Often confused with
Rostite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside rostite
Minerals reported to co-occur with rostite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Al(SO₄)F·5H₂O
- Mohs hardness
- 2
- Density
- 2.05 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Prismatic Crystals, Coatings, Crusts
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Burning Coal Mine Dumps, Fumarole Deposits
- Typical price
- $20-100 per specimen
Where rockhounds find rostite
Classic worldwide localities
- Kladno, Czech Republic
- Kamchatka, Russia
- Banská Štiavnica, Slovakia
Field-hunting tip
Look in burning coal mine dumps, fumarole deposits country — that is the host setting where rostite typically forms. If you start seeing gypsum, alunogen, sulfur in float, you are in the right ground. Field specimens usually show a prismatic crystals, coatings, crusts habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find rostite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
