Duranusite is an extremely rare arsenic sulfide mineral that typically occurs as small, dark lead-gray to black masses within hydrothermal vein deposits. It is primarily known from its type locality in France and is highly prized by advanced mineral collectors for its chemical composition and scarcity.
Is this duranusite?
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 duranusite with a known reference. Duranusite sits at Mohs 1.5-2 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Duranusite leaves a black streak.
- 3Read the lusterHold the specimen under a strong light. Duranusite typically shows a metallic luster.
- 4Match the color rangeCompare against the expected color range: dark lead-gray, black.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: massive, granular, or thin crusts.
Often confused with
Duranusite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Duranusite leaves black, Realgar leaves orange-red; luster reads metallic on Duranusite and resinous on Realgar.
How to tell apart: Streak differs — Duranusite leaves black, Orpiment leaves yellow; luster reads metallic on Duranusite and resinous on Orpiment.
How to tell apart: Streak differs — Duranusite leaves black, Stibnite leaves lead-gray.
Often found alongside duranusite
Minerals reported to co-occur with duranusite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- As₄S
- Mohs hardness
- 1.5-2
- Density
- 6.1-6.2 g/cm³
- Colors
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Massive, Granular, Or Thin Crusts
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Veins
- Typical price
- $50-300 per specimen
Where rockhounds find duranusite
Classic worldwide localities
- Duranus, France
- Allchar, North Macedonia
- Tajikistan
Field-hunting tip
Look in hydrothermal veins country — that is the host setting where duranusite typically forms. If you start seeing realgar, orpiment, calcite in float, you are in the right ground. Field specimens usually show a massive, granular, or thin crusts habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find duranusite on the map
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