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. Streak: light green.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: bottle green.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: aggregates.
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 to brown; luster reads vitreous on Rollandite and adamantine to vitreous, pearly to silky if fibrous 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
- Bottle green
- Streak
- Light green
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Aggregates
- Cleavage
- Good on {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A secondary mineral in small geodes
Where rockhounds find rollandite
Classic worldwide localities
- Cu mines of Roua at the western margin of the Barrot Dome, Alpes-Maritimes, France (type locality)
Field-hunting tip
Where it forms: A secondary mineral in small geodes. If you start seeing olivenite, conichalcite, clinotyrolite in float, you are in the right ground. Typical habit: aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify rollandite?+
Where is rollandite found?+
Is rollandite safe to handle?+
What rocks look like rollandite?+
What minerals are found with rollandite?+
What kind of rock does rollandite form in?+
What is rollandite used for?+
Find rollandite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
