Tavagnascoite is a very rare bismuth sulfate mineral found primarily in the hydrothermal deposits of Tavagnasco, Italy. It typically occurs as delicate, pale yellow tabular crystals or radiating aggregates associated with bismuthinite and pyrite.
Is this tavagnascoite?
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 tavagnascoite with a known reference. Tavagnascoite 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. Tavagnascoite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Tavagnascoite typically shows a adamantine luster.
- 4Match the color rangeCompare against the expected color range: yellow, pale yellow.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: tabular crystals, radiating aggregates.
Often confused with
Tavagnascoite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Bismutite is the harder of the two (Mohs 3 vs. 2); luster reads adamantine on Tavagnascoite and pearly on Bismutite.
How to tell apart: Beyerite is the harder of the two (Mohs 3 vs. 2); luster reads adamantine on Tavagnascoite and pearly on Beyerite.
Often found alongside tavagnascoite
Minerals reported to co-occur with tavagnascoite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Bi₄O₄(SO₄)(OH)₂
- Mohs hardness
- 2
- Density
- 4.26 g/cm³
- Colors
- Streak
- White
- Luster
- Adamantine
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Tabular Crystals, Radiating Aggregates
- Cleavage
- Perfect in One Direction
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Veins
- Typical price
- $100-500 for small thumbnail specimens
Where rockhounds find tavagnascoite
Classic worldwide localities
- Tavagnasco, Aosta Valley, Italy
Field-hunting tip
Look in hydrothermal veins country — that is the host setting where tavagnascoite typically forms. If you start seeing bismuthinite, pyrite, quartz in float, you are in the right ground. Field specimens usually show a tabular crystals, radiating aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find tavagnascoite on the map
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