Rollandite is an extremely rare arsenate mineral that typically forms as delicate, bottle-green bladed crystals. It is primarily found in oxidized zones of arsenic-rich base metal deposits and is highly sought after by advanced collectors for its distinct color and scarcity.
Is this rollandite?
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 rollandite with a known reference. Rollandite sits at Mohs 4-4.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Rollandite leaves a light green streak.
- 3Read the lusterHold the specimen under a strong light. Rollandite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: bottle-green.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: bladed to acicular crystals.
Often confused with
Rollandite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Rollandite leaves light green, Cornubite leaves pale green.
How to tell apart: Rollandite is noticeably harder (Mohs 4-4.5 vs. 3); streak differs, so Rollandite leaves light green, Olivenite leaves olive-green; luster reads vitreous on Rollandite and adamantine on Olivenite.
Often found alongside rollandite
Minerals reported to co-occur with rollandite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Cu₃(AsO₄)₂·4H₂O
- Mohs hardness
- 4-4.5
- Density
- 3.9 g/cm³
- Colors
- Streak
- Light Green
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Bladed to Acicular Crystals
- Cleavage
- Perfect On {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Vein Deposits in Sandstone or Metamorphic Rocks
Where rockhounds find rollandite
Classic worldwide localities
- Cap Garonne, France
- Schneeberg, Germany
Field-hunting tip
Look in hydrothermal vein deposits in sandstone or metamorphic rocks country, the host setting where rollandite typically forms. If you start seeing tennantite, olivenite, cornubite in float, you are in the right ground. Field specimens usually show a bladed to acicular crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find rollandite on the map
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