Bernarlottiite is an extremely rare lead-arsenic sulfosalt found almost exclusively in the famous Lengenbach Quarry in Switzerland. It occurs as small, dark, metallic platy crystals embedded within dolomitic marble, often requiring microscopic examination for positive identification.

Hardness

3-3.5

Mohs

Luster

Metallic

Streak

Black

Transparency

Opaque

mineralrare

Bernarlottiite

Hardness: 3-3.5
Luster: Metallic
Streak: Black
Transparency: Opaque

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Is this bernarlottiite?

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 bernarlottiite with a known reference. Bernarlottiite sits at Mohs 3-3.5, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: black.
3
Read the luster
Hold the specimen under a strong light. Luster: metallic.
4
Match the color range
Compare against the expected color range: lead-gray.
5
Look at form & habit
Crystal system: triclinic. Typical habit: platy crystals.

Often confused with

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

mineral

Sartorite

Mohs 3

How to tell apart: Streak differs, so Bernarlottiite leaves black, Sartorite leaves chocolate-brown.

How to tell apart: Streak differs, so Bernarlottiite leaves black, Baumhauerite leaves chocolate-brown.

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All properties

Chemical formula: Pb₁₂(As₁₀Sb₆)S₃₆
Mohs hardness: 3-3.5
Density: 5.601 g/cm³
Colors: Lead-gray
Streak: Black
Luster: Metallic
Transparency: Opaque
Crystal system: Triclinic
Crystal habit: Platy crystals
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Of hydrothermal origin in cavities, to 30 cm, in marble related to tectonometamorphism

Where rockhounds find bernarlottiite

Classic worldwide localities

Ceragiola quarry, Seravezza, Apuan Alps, Tuscany, Italy

Field-hunting tip

Where it forms: Of hydrothermal origin in cavities, to 30 cm, in marble related to tectonometamorphism. If you start seeing sb-rich sartorite in float, you are in the right ground. Typical habit: platy crystals. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify bernarlottiite?+

Mohs hardness is 3-3.5. Luster: metallic. The streak is black. Common colors include lead-gray.

Where is bernarlottiite found?+

Notable localities include Ceragiola quarry, Seravezza, Apuan Alps, Tuscany, Italy.

Is bernarlottiite safe to handle?+

Bernarlottiite contains antimony, arsenic and lead and calls for real care. Contains lead and arsenic; wash hands thoroughly after handling and avoid inhaling dust.

What rocks look like bernarlottiite?+

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

What minerals are found with bernarlottiite?+

Bernarlottiite commonly co-occurs with Sb-rich sartorite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does bernarlottiite form in?+

Where it forms: Of hydrothermal origin in cavities, to 30 cm, in marble related to tectonometamorphism. Working float back to the host body is the standard way to chase a fresh occurrence.

What is bernarlottiite used for?+

Bernarlottiite is used in collector.

Find bernarlottiite on the map

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