Bílinite is a rare hydrated iron aluminum sulfate typically found as fragile fibrous efflorescences or needles in oxidized coal mine tailings. It is highly soluble in water and dehydrates easily upon exposure to dry air, making it a difficult mineral to preserve in collections.
Is this bílinite?
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 bílinite with a known reference. Bílinite 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. Bílinite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Bílinite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, colorless, pale yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: fibrous, efflorescent crusts, acicular needles.
Often confused with
Bílinite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside bílinite
Minerals reported to co-occur with bílinite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Fe²⁺Al₂(SO₄)₄·22H₂O
- Mohs hardness
- 2
- Density
- 1.8-1.9 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Fibrous, Efflorescent Crusts, Acicular Needles
- Cleavage
- Perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Coal-bearing Shale or Sedimentary Formations Containing Pyrite
- Typical price
- $20-100 for small specimen
Where rockhounds find bílinite
Classic worldwide localities
- Bílina, Czech Republic
- Jáchymov, Czech Republic
- Hluboká, Czech Republic
- Klodzko, Poland
Field-hunting tip
Look in oxidized coal-bearing shale or sedimentary formations containing pyrite country — that is the host setting where bílinite typically forms. If you start seeing gypsum, melanterite, alunogen in float, you are in the right ground. Field specimens usually show a fibrous, efflorescent crusts, acicular needles habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find bílinite on the map
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