Felsőbányaite is a rare secondary sulfate mineral typically found as pearly white crusts or delicate platy aggregates within mine workings. It forms through the alteration of aluminum-bearing minerals in sulfide deposits and is highly prized by collectors for its fragile, tabular crystal habits.
Is this felsőbányaite?
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 felsőbányaite with a known reference. Felsőbányaite sits at Mohs 1.5, 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: vitreous, pearly on cleavages.
- 4Match the color rangeCompare against the expected color range: white, colorless, yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: aggregates, globular, radial.
Often confused with
Felsőbányaite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads vitreous, pearly on cleavages on Felsőbányaite and subvitreous, pearly on {010} cleavages, silky if fibrous on Gypsum.
How to tell apart: Luster reads vitreous, pearly on cleavages on Felsőbányaite and pearly to dull earthy on Kaolinite.
Often found alongside felsőbányaite
Minerals reported to co-occur with felsőbányaite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Al₄SO₄(OH)₁₀·4H₂O
- Mohs hardness
- 1.5
- Density
- 2.33-2.35 g/cm³
- Streak
- White
- Luster
- Vitreous, pearly on cleavages
- Transparency
- Semitransparent
- Crystal system
- Monoclinic
- Crystal habit
- Aggregates, globular, radial
- Cleavage
- {001}, perfect; {100} and {010}, observed
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A rare product of oxidation of marcasite ores
Where rockhounds find felsőbányaite
Classic worldwide localities
- Cavnic (Kapnikbánya), near Baia Sprie, Romania
Field-hunting tip
Where it forms: A rare product of oxidation of marcasite ores. If you start seeing marcasite, stibnite, barite in float, you are in the right ground. Typical habit: aggregates, globular, radial. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify felsőbányaite?+
Where is felsőbányaite found?+
What rocks look like felsőbányaite?+
What minerals are found with felsőbányaite?+
What kind of rock does felsőbányaite form in?+
What is felsőbányaite used for?+
Find felsőbányaite on the map
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