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

Streak

Black

Transparency

Opaque

mineralrare

Spaltiite

Hardness: 2.5-3
Luster: Metallic
Streak: Black
Transparency: Opaque

Is this spaltiite?

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 spaltiite with a known reference. Spaltiite sits at Mohs 2.5-3, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Spaltiite leaves a black streak.
3
Read the luster
Hold the specimen under a strong light. Spaltiite typically shows a metallic luster.
4
Match the color range
Compare against the expected color range: lead-gray, black.
5
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: Streak differs, so Spaltiite leaves black, Proustite leaves scarlet; luster reads metallic on Spaltiite and adamantine on Proustite.

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

How to tell apart: Streak differs, so Spaltiite leaves black, Dufrénoysite leaves reddish-brown.

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: Ag₂AsS₃
Mohs hardness: 2.5-3
Density: 5.68 g/cm³
Colors: Lead-gray Black
Streak: Black
Luster: Metallic
Transparency: Opaque
Crystal system: Monoclinic
Crystal habit: Massive, Anhedral Grains
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Dolomitic Marble
Typical price: $100-500 per specimen

Where rockhounds find spaltiite

Classic worldwide localities

Lengenbach Quarry, Binn Valley, Switzerland

Field-hunting tip

Look in dolomitic marble country, the host setting where spaltiite typically forms. If you start seeing sartorite, dufrénoysite, realgar in float, you are in the right ground. Field specimens usually show a massive, anhedral grains habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify spaltiite?+

Mohs hardness is 2.5-3. It typically shows a metallic luster. The streak is black. Common colors include lead-gray, black.

Where is spaltiite found?+

Notable localities include Lengenbach Quarry, Binn Valley, Switzerland.

How much is spaltiite worth?+

Typical asking prices fall in the range of $100-500 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

Is spaltiite safe to handle?+

It contains toxic constituents. Contains arsenic, which is toxic if inhaled or ingested. Wash hands thoroughly after handling and avoid creating dust when prepping or breaking specimens. Handle with care, avoid grinding or breathing dust, and store separately.

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?+

Spaltiite typically forms in 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.