Fiemmeite is a rare copper oxalate mineral originally discovered in the copper-bearing sandstone deposits of the Fiemme Valley in Italy. It typically forms delicate, sky-blue platy crystals or crusts within the matrix of sedimentary rocks. Due to its extreme rarity and fragile nature, it is primarily sought after by advanced mineral collectors and those interested in organic-inorganic mineral species.
Is this fiemmeite?
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 fiemmeite with a known reference. Fiemmeite 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: pale blue.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous to waxy.
- 4Match the color rangeCompare against the expected color range: sky-blue.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: platy crystals, crusts, aggregates.
Often confused with
Fiemmeite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Fiemmeite leaves pale blue, Moolooite leaves light blue; luster reads vitreous to waxy on Fiemmeite and dull to waxy on Moolooite.
How to tell apart: Weddellite is the harder of the two (Mohs ~4 vs. 2); streak differs, so Fiemmeite leaves pale blue, Weddellite leaves white.
Often found alongside fiemmeite
Minerals reported to co-occur with fiemmeite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Cu₂(C₂O₄)(OH)₂·2H₂O
- Mohs hardness
- 2
- Density
- 2.78 g/cm³
- Colors
- Streak
- Pale blue
- Luster
- Vitreous to waxy
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Platy crystals, crusts, aggregates
- Cleavage
- Almost perfect on {010} or {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In coalified wood trunks in continental sandstone which were permeated by mineralizing solutions containing Cu, U, As, Pb and Zn
Where rockhounds find fiemmeite
Classic worldwide localities
- Fiemme Valley, Trentino-Alto Adige, Italy
Field-hunting tip
Where it forms: In coalified wood trunks in continental sandstone which were permeated by mineralizing solutions containing Cu, U, As, Pb and Zn. If you start seeing baryte, olivenite, middlebackite in float, you are in the right ground. Typical habit: platy crystals, crusts, aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify fiemmeite?+
Where is fiemmeite found?+
Is fiemmeite safe to handle?+
What rocks look like fiemmeite?+
What minerals are found with fiemmeite?+
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Find fiemmeite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
