Quadratite is an extremely rare sulfosalt mineral primarily found in the famous Lengenbach Quarry of Switzerland. It typically appears as tiny, thin, tetragonal plates with a distinct adamantine luster, often requiring magnification for proper identification. Due to its complex chemistry and scarcity, it is highly sought after by advanced mineral collectors.
Is this quadratite?
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 quadratite with a known reference. Quadratite sits at Mohs 3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: reddish brown.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic in thick laminae.
- 4Match the color rangeCompare against the expected color range: gray, reddish gray.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: microscopic crystals, tabular.
Often confused with
Quadratite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Quadratite leaves reddish brown, Proustite leaves vermilion; luster reads metallic in thick laminae on Quadratite and adamantine on Proustite.
How to tell apart: Streak differs, so Quadratite leaves reddish brown, Pyrargyrite leaves purplish red; luster reads metallic in thick laminae on Quadratite and adamantine on Pyrargyrite.
Often found alongside quadratite
Minerals reported to co-occur with quadratite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- AgCdAsS₃
- Mohs hardness
- 3
- Density
- 5.31 g/cm³
- Colors
- Streak
- Reddish brown
- Luster
- Metallic in thick laminae
- Transparency
- Translucent on thin edges to opague
- Crystal system
- Tetragonal
- Crystal habit
- Microscopic crystals, tabular
- Cleavage
- Perfect on {001}, distinct on {110}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In cavities in hydrothermally altered dolostone, likely formed at a late stage
Where rockhounds find quadratite
Classic worldwide localities
- Lengenbach, Binntal, Switzerland
Field-hunting tip
Where it forms: In cavities in hydrothermally altered dolostone, likely formed at a late stage. If you start seeing galena, jordanite, pyrite in float, you are in the right ground. Typical habit: microscopic crystals, tabular. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify quadratite?+
Where is quadratite found?+
Is quadratite safe to handle?+
What rocks look like quadratite?+
What minerals are found with quadratite?+
What kind of rock does quadratite form in?+
What is quadratite used for?+
Find quadratite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
