Tavagnascoite is a very rare bismuth sulfate mineral found primarily in the hydrothermal deposits of Tavagnasco, Italy. It typically occurs as delicate, colorless tabular crystals or radiating aggregates associated with bismuthinite and pyrite.

Hardness

Mohs

Luster

Silky

Transparency

Transparent to translucent

mineralrare

Tavagnascoite

Hardness: 2
Luster: Silky
Transparency: Transparent to translucent

No image

Is this tavagnascoite?

4-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch tavagnascoite with a known reference. Tavagnascoite sits at Mohs 2, softer than the next harder reference, harder than the previous one.
2
Read the luster
Hold the specimen under a strong light. Luster: silky.
3
Match the color range
Compare against the expected color range: colorless.
4
Look at form & habit
Crystal 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.

mineral

Bismutite

Mohs 2.5-3.5

How to tell apart: Luster reads silky on Tavagnascoite and vitreous, waxy, may be dull to earthy on Bismutite.

How to tell apart: Luster reads silky on Tavagnascoite and vitreous on Beyerite.

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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.

Quartz
mineral · Mohs 7

All properties

Chemical formula: Bi₄O₄(SO₄)(OH)₂
Mohs hardness: 2
Density: 6.505 g/cm³
Colors: Colorless
Luster: Silky
Transparency: Transparent to translucent
Crystal system: Orthorhombic
Crystal habit: Tabular crystals, radiating aggregates
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Within vugs in hydrothermal veins,in association with secondary Bi-minerals from the alteration of a bismuthinite ± Bi-sulfosalt assemblage

Where rockhounds find tavagnascoite

Classic worldwide localities

Espérance superiore tunnel, Tavagnasco ore district, Alto Canavese region, 50 km north of Turin, Piedmont, Italy

Field-hunting tip

Where it forms: Within vugs in hydrothermal veins,in association with secondary Bi-minerals from the alteration of a bismuthinite ± Bi-sulfosalt assemblage. If you start seeing quartz, bi-oxides and sulfates in float, you are in the right ground. Typical habit: tabular crystals, radiating aggregates. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify tavagnascoite?+

Mohs hardness is 2. Luster: silky. Common colors include colorless.

Where is tavagnascoite found?+

Notable localities include Espérance superiore tunnel, Tavagnasco ore district, Alto Canavese region, 50 km north of Turin, Piedmont, Italy.

Is tavagnascoite safe to handle?+

Contains bismuth; avoid inhalation of dust or ingestion. Wash hands thoroughly after handling.

What rocks look like tavagnascoite?+

Tavagnascoite is most often confused with Bismutite, Beyerite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with tavagnascoite?+

Tavagnascoite commonly co-occurs with Quartz, Bi-oxides and sulfates. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does tavagnascoite form in?+

Where it forms: Within vugs in hydrothermal veins,in association with secondary Bi-minerals from the alteration of a bismuthinite ± Bi-sulfosalt assemblage. Working float back to the host body is the standard way to chase a fresh occurrence.

What is tavagnascoite used for?+

Tavagnascoite is used in collector.

Find tavagnascoite on the map

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