Spaltiite is an extremely rare sulfosalt mineral found almost exclusively in the famous Lengenbach Quarry in Switzerland. It is best identified through laboratory analysis of metallic, lead-gray aggregates associated with other complex arsenic-bearing minerals in metamorphosed dolomitic marble.

Hardness

2.5-3

Mohs

Luster

Metallic

Transparency

Opaque

mineralrare

Spaltiite

Hardness: 2.5-3
Luster: Metallic
Transparency: Opaque

Is this spaltiite?

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 spaltiite with a known reference. Spaltiite sits at Mohs 2.5-3, softer than the next harder reference, harder than the previous one.
2
Read the luster
Hold the specimen under a strong light. Luster: metallic.
3
Match the color range
Compare against the expected color range: lead-gray, black.
4
Look at form & habit
Crystal system: monoclinic. Typical habit: massive, anhedral grains.

Often confused with

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

mineral

Proustite

Mohs 2-2.5

How to tell apart: Luster reads metallic on Spaltiite and adamantine on Proustite.

How to tell apart: Luster reads metallic on Spaltiite and submetallic on Dufrénoysite.

Compare →

Often found alongside spaltiite

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

All properties

Chemical formula: Tl₂Cu₂As₂S₅
Mohs hardness: 2.5-3
Colors: Lead-gray Black
Luster: Metallic
Transparency: Opaque
Crystal system: Monoclinic
Crystal habit: Massive, anhedral grains
Rarity: Rare
Uses: Collector
Host rock: dolomitic marble

Where rockhounds find spaltiite

Classic worldwide localities

Lengenbach quarry, Im Feld, Binntal, Canton Wallis, Switzerland

Field-hunting tip

Where it forms: dolomitic marble. If you start seeing sartorite, dufrénoysite, realgar in float, you are in the right ground. Typical habit: massive, anhedral grains. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify spaltiite?+

Mohs hardness is 2.5-3. Luster: metallic. Common colors include lead-gray, black.

Where is spaltiite found?+

Notable localities include Lengenbach quarry, Im Feld, Binntal, Canton Wallis, Switzerland.

Is spaltiite safe to handle?+

Spaltiite contains arsenic, copper and thallium and calls for real care. Contains arsenic, which is toxic if inhaled or ingested. Wash hands thoroughly after handling and avoid creating dust when prepping or breaking specimens.

What rocks look like spaltiite?+

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

What minerals are found with spaltiite?+

Spaltiite commonly co-occurs with Sartorite, Dufrénoysite, Realgar, Pyrite, Galena. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does spaltiite form in?+

Where it forms: dolomitic marble. Working float back to the host body is the standard way to chase a fresh occurrence.

What is spaltiite used for?+

Spaltiite is used in collector.

Find spaltiite on the map

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