Brushite is a phosphate mineral primarily forming through the alteration of guano deposits in arid environments or caves. It often appears as small, fragile, tabular or bladed white crystals that require careful handling due to their low hardness and sensitivity to hydration changes.
Is this brushite?
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 brushite with a known reference. Brushite 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, pearly on cleavages.
- 4Match the color rangeCompare against the expected color range: white, colorless, yellow, yellowish white.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular crystals, bladed, sometimes massive or earthy.
Often confused with
Brushite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside brushite
Minerals reported to co-occur with brushite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaHPO₄·2H₂O
- Mohs hardness
- 2.5
- Density
- 2.328 g/cm³
- Streak
- White
- Luster
- Vitreous, pearly on cleavages
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular crystals, bladed, sometimes massive or earthy
- Cleavage
- On {010} and {001}, perfect
- Rarity
- Uncommon
- Uses
- Collector, Scientific research
- Host rock
- One of the most common cave minerals, in guano deposits, and in phosphorites, formed at low pH by reaction of phosphate-rich solutions with calcite and clay
Where rockhounds find brushite
Classic worldwide localities
- Pig Hole Cave, Giles Co., Virginia, USA
- Rock Creek, Kankakee Co., Illinois, USA
- Kartchner Cavern, near Benson, Cochise Co., Arizona, USA
- Found on Aves Island, Venezuela, west of Dominica in the Caribbean Sea
- Sombrero Island, West Indies
- Mona Island, Puerto Rico
Field-hunting tip
Where it forms: One of the most common cave minerals, in guano deposits, and in phosphorites, formed at low pH by reaction of phosphate-rich solutions with calcite and clay. If you start seeing tanarakite, ardealite, hydroxylapatite in float, you are in the right ground. Typical habit: tabular crystals, bladed, sometimes massive or earthy. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify brushite?+
Where is brushite found?+
What rocks look like brushite?+
What minerals are found with brushite?+
What kind of rock does brushite form in?+
What is brushite used for?+
Find brushite on the map
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