Sardignaite is a rare bismuth molybdate, typically pale yellow. It was approved as a distinct mineral species in 2008. It was first described from Su Senargiu, near Sarroch, Sardegna, Italy.

Hardness

Mohs

Luster

Adamantine

Streak

White

Transparency

Transparent

mineralrare

Sardignaite

Sardignaite is a rare bismuth molybdate, typically pale yellow. It was approved as a distinct mineral species in 2008. It was first described from Su Senargiu, near Sarroch, Sardegna, Italy.

Hardness: ~3
Luster: Adamantine
Streak: White
Transparency: Transparent

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Is this sardignaite?

5-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 sardignaite with a known reference. Sardignaite sits at Mohs ~3, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: white.
3
Read the luster
Hold the specimen under a strong light. Luster: adamantine.
4
Match the color range
Compare against the expected color range: pale yellow.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: tabular crystals, crusts, aggregates.

Often confused with

Sardignaite vs. its common look-alikes, and how to tell them apart in the field.

Often found alongside sardignaite

Minerals reported to co-occur with sardignaite. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: BiMo₂O₇(OH)·2H₂O
Mohs hardness: ~3
Density: 4.82 g/cm³
Colors: Pale yellow
Streak: White
Luster: Adamantine
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Tabular crystals, crusts, aggregates
Rarity: Rare
Uses: Collector
Host rock: A secondary mineral formed in the oxidation zone of a molybdenite-bismuthinite deposit in quartz veins within a granite

Where rockhounds find sardignaite

Classic worldwide localities

Su Senargiu, near Sarroch, Sardegna, Italy

Field-hunting tip

Where it forms: A secondary mineral formed in the oxidation zone of a molybdenite-bismuthinite deposit in quartz veins within a granite. If you start seeing bismuthinite, bismoclite, molybdenite in float, you are in the right ground. Typical habit: tabular crystals, crusts, aggregates. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify sardignaite?+

Mohs hardness is ~3. Luster: adamantine. The streak is white. Common colors include pale yellow.

Where is sardignaite found?+

Notable localities include Su Senargiu, near Sarroch, Sardegna, Italy.

Is sardignaite safe to handle?+

Contains bismuth, which is toxic if ingested or inhaled as dust. Wash hands thoroughly after handling and avoid creating dust.

What rocks look like sardignaite?+

Sardignaite is most often confused with Anglesite, Cerussite, Lanarkite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with sardignaite?+

Sardignaite commonly co-occurs with Bismuthinite, Bismoclite, Molybdenite, Ferrimolybdite, Koechlinite, Wulfenite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does sardignaite form in?+

Where it forms: A secondary mineral formed in the oxidation zone of a molybdenite-bismuthinite deposit in quartz veins within a granite. Working float back to the host body is the standard way to chase a fresh occurrence.

What is sardignaite used for?+

Sardignaite is used in collector.

Find sardignaite on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.