Duranusite is an extremely rare arsenic sulfide mineral that typically occurs as small, red 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 2, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: black.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: red.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: microscopic crystals.
Often confused with
Duranusite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Duranusite leaves black, Realgar leaves red-orange to red; luster reads metallic on Duranusite and resinous to greasy on Realgar.
How to tell apart: Streak differs, so Duranusite leaves black, Orpiment leaves pale lemon-yellow; luster reads metallic on Duranusite and resinous, pearly on cleavage surface on Orpiment.
How to tell apart: Streak differs, so 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
- 2
- Density
- 4.5 g/cm³
- Colors
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Microscopic crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In calcite veinlets in marls and siliceous limestones (Duranus, France)
Where rockhounds find duranusite
Classic worldwide localities
- Duranus, Alpes-Maritimes, France (type locality)
- Mt. Washington copper mine, Vancouver Island, British Columbia, Canada
- Capillitas mine, San Luis, Catamarca Province, Argentina
Field-hunting tip
Where it forms: In calcite veinlets in marls and siliceous limestones (Duranus, France). If you start seeing arsenic, realgar, orpiment in float, you are in the right ground. Typical habit: microscopic crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify duranusite?+
Where is duranusite found?+
Is duranusite safe to handle?+
What rocks look like duranusite?+
What minerals are found with duranusite?+
What kind of rock does duranusite form in?+
What is duranusite used for?+
Find duranusite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
