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. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: silky.
- 4Match the color rangeCompare against the expected color range: white, yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: fibrous, radial.
Often confused with
Bílinite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads silky on Bílinite and vitreous to silky on Alunogen.
How to tell apart: Luster reads silky on Bílinite and vitreous on Halotrichite.
How to tell apart: Luster reads silky on Bílinite and vitreous on Melanterite.
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
- FeFe₂(SO₄)₄·22H₂O
- Mohs hardness
- ~2
- Density
- 1.875-1.99 g/cm³
- Streak
- White
- Luster
- Silky
- Transparency
- Semitransparent
- Crystal system
- Monoclinic
- Crystal habit
- Fibrous, radial
- Cleavage
- Perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- An alteration of iron sulfide in lignite (Světec, Czech Republic); a post-mine mineral with other iron sulfates (Nikitov deposits, Ukraine)
Where rockhounds find bílinite
Classic worldwide localities
- Higgins mine, Bisbee, Cochise Co., Arizona, and at Arco, Butte Co., Idaho, USA
- Světec (Schwaz), near Bílina, Czech Republic
- Nikitov mercury deposits, Ukraine
- Chiricas mine, Malargüe district, Mendoza Province, Argentina
Field-hunting tip
Where it forms: An alteration of iron sulfide in lignite (Světec, Czech Republic); a post-mine mineral with other iron sulfates (Nikitov deposits, Ukraine). If you start seeing melanterite in float, you are in the right ground. Typical habit: fibrous, radial. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify bílinite?+
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What rocks look like bílinite?+
What minerals are found with bílinite?+
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Find bílinite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
