Ceruleite is a rare copper aluminum arsenate mineral typically found as soft, sky-blue massive crusts or botryoidal forms within oxidized copper deposits. Collectors value it for its vibrant color, though it is usually opaque and requires careful handling due to its arsenic content.
Is this ceruleite?
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 ceruleite with a known reference. Ceruleite sits at Mohs 5-6 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Ceruleite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Ceruleite typically shows a dull luster.
- 4Match the color rangeCompare against the expected color range: blue, sky-blue, pale blue.
- 5Look at form & habitCrystal system: triclinic. Typical habit: massive, crusts, botryoidal.
Often confused with
Ceruleite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Luster reads dull on Ceruleite and waxy on Turquoise.
How to tell apart: Ceruleite is noticeably harder (Mohs 5-6 vs. 2-4); luster reads dull on Ceruleite and vitreous on Chrysocolla.
How to tell apart: Luster reads dull on Ceruleite and waxy on Variscite.
Often found alongside ceruleite
Minerals reported to co-occur with ceruleite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CuAl₆(AsO₄)₄(OH)₈·2H₂O
- Mohs hardness
- 5-6
- Density
- 2.8-2.9 g/cm³
- Streak
- White
- Luster
- Dull
- Transparency
- Opaque
- Crystal system
- Triclinic
- Crystal habit
- Massive, Crusts, Botryoidal
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector, Lapidary
- Host rock
- Oxidized Copper Ore Deposits
- Typical price
- $20-150 for small specimens depending on quality and origin.
Where rockhounds find ceruleite
Classic worldwide localities
- Chuquicamata Mine, Chile
- Utah, USA
- Nevada, USA
Field-hunting tip
Look in oxidized copper ore deposits country — that is the host setting where ceruleite typically forms. If you start seeing copper, quartz, goethite in float, you are in the right ground. Field specimens usually show a massive, crusts, botryoidal habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find ceruleite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
