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, so Quadratite leaves yellowish-orange, Proustite leaves scarlet.
How to tell apart: Quadratite is noticeably harder (Mohs 3.5 vs. 2.5); streak differs, so 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, 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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