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.
Is this spaltiite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry 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.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Spaltiite leaves a black streak.
- 3Read the lusterHold the specimen under a strong light. Spaltiite typically shows a metallic luster.
- 4Match the color rangeCompare against the expected color range: lead-gray, black.
- 5Look at form & habitCrystal 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.
How to tell apart: Streak differs — Spaltiite leaves black, Proustite leaves scarlet; luster reads metallic on Spaltiite and adamantine on Proustite.
How to tell apart: Streak differs — Spaltiite leaves black, Sartorite leaves chocolate-brown.
How to tell apart: Streak differs — Spaltiite leaves black, Dufrénoysite leaves reddish-brown.
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
- 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 — that is 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?+
Where is spaltiite found?+
How much is spaltiite worth?+
Is spaltiite safe to handle?+
What rocks look like spaltiite?+
What minerals are found with spaltiite?+
What kind of rock does spaltiite form in?+
What is spaltiite used for?+
Find spaltiite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
