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 3.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Quadratite leaves a yellowish-orange streak.
- 3Read the lusterHold the specimen under a strong light. Quadratite typically shows a adamantine luster.
- 4Match the color rangeCompare against the expected color range: red, brownish-red.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: tabular crystals, thin plates.
Often confused with
Quadratite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Quadratite is noticeably harder (Mohs 3.5 vs. 2-2.5); streak differs — Quadratite leaves yellowish-orange, Proustite leaves scarlet.
How to tell apart: Quadratite is noticeably harder (Mohs 3.5 vs. 2.5); streak differs — Quadratite leaves yellowish-orange, Pyrargyrite leaves red; luster reads adamantine on Quadratite and metallic to 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
- Ag(Cd,Pb)AsS₃
- Mohs hardness
- 3.5
- Density
- 7.5 g/cm³
- Colors
- Streak
- Yellowish-orange
- Luster
- Adamantine
- Transparency
- Translucent
- Crystal system
- Tetragonal
- Crystal habit
- Tabular Crystals, Thin Plates
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Dolomitic Marble
- Typical price
- $200-2000 per specimen
Where rockhounds find quadratite
Classic worldwide localities
- Lengenbach Quarry, Binn Valley, Switzerland
Field-hunting tip
Look in dolomitic marble country — that is the host setting where quadratite typically forms. If you start seeing realgar, arsenopyrite, sartorite in float, you are in the right ground. Field specimens usually show a tabular crystals, thin plates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find quadratite on the map
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