Fianelite is an extremely rare copper magnesium arsenate mineral first discovered in the Fianel mine in Switzerland. It typically forms as small, bright yellow tabular crystals within dolomitic marble deposits. Due to its rarity and complex arsenic chemistry, it is highly sought after by advanced systematic mineral collectors.
Is this fianelite?
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 fianelite with a known reference. Fianelite sits at Mohs 3.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Fianelite leaves a yellow streak.
- 3Read the lusterHold the specimen under a strong light. Fianelite typically shows a adamantine luster.
- 4Match the color rangeCompare against the expected color range: yellow, orange-yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular crystals.
Often confused with
Fianelite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Fianelite leaves yellow, Austinite leaves white; luster reads adamantine on Fianelite and vitreous on Austinite.
How to tell apart: Conichalcite is the harder of the two (Mohs 4.5 vs. 3.5); streak differs — Fianelite leaves yellow, Conichalcite leaves light green; luster reads adamantine on Fianelite and vitreous on Conichalcite.
Often found alongside fianelite
Minerals reported to co-occur with fianelite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Cu₂Mg(AsO₄)(OH)₃
- Mohs hardness
- 3.5
- Density
- 4.87 g/cm³
- Colors
- Streak
- Yellow
- Luster
- Adamantine
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular Crystals
- Cleavage
- Good
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Dolomitic Marbles
- Typical price
- $100-500 per specimen
Where rockhounds find fianelite
Classic worldwide localities
- Fianel mine, Val Ferrera, Switzerland
Field-hunting tip
Look in dolomitic marbles country — that is the host setting where fianelite typically forms. If you start seeing arsenates, dolomite in float, you are in the right ground. Field specimens usually show a tabular crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find fianelite on the map
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