Caminite is a rare magnesium sulfate hydroxide mineral formed primarily in hydrothermal vent settings on the ocean floor. It typically occurs as white to colorless platy crystals associated with anhydrite and metallic sulfides in deep-sea environments.
Is this caminite?
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 caminite with a known reference. Caminite sits at Mohs 2.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: white, colorless.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: platy crystals, crusts, or globular aggregates.
Often confused with
Caminite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads vitreous on Caminite and pearly on {010}, vitreous to greasy on {001}; vitreous on {100} on Anhydrite.
How to tell apart: Luster reads vitreous on Caminite and subvitreous, pearly on {010} cleavages, silky if fibrous on Gypsum.
How to tell apart: Luster reads vitreous on Caminite and earthy on Bassanite.
Often found alongside caminite
Minerals reported to co-occur with caminite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Mg₇(SO₄)₅(OH)₄·H₂O
- Mohs hardness
- 2.5
- Density
- 2.58-2.79 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Tetragonal
- Crystal habit
- Platy crystals, crusts, or globular aggregates
- Cleavage
- {001}, good, possible
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Formed by the reaction of sea water with hydrothermal fluids in a midocean ridge submarine chimney vent
Where rockhounds find caminite
Classic worldwide localities
- Along the East Pacific Rise at 21deg N Lat (type locality)
Field-hunting tip
Where it forms: Formed by the reaction of sea water with hydrothermal fluids in a midocean ridge submarine chimney vent. If you start seeing anhydrite in float, you are in the right ground. Typical habit: platy crystals, crusts, or globular aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify caminite?+
Where is caminite found?+
What rocks look like caminite?+
What minerals are found with caminite?+
What kind of rock does caminite form in?+
What is caminite used for?+
Find caminite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
