Monetite is a rare phosphate mineral primarily found in guano-rich cave environments where it forms through the dehydration of brushite. It typically presents as white to colorless tabular crystals or crusts that are often associated with other calcium phosphates.
Is this monetite?
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 monetite with a known reference. Monetite sits at Mohs 3.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Monetite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Monetite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, colorless, gray, yellowish.
- 5Look at form & habitCrystal system: triclinic. Typical habit: tabular crystals, massive, granular, crusts.
Often confused with
Monetite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside monetite
Minerals reported to co-occur with monetite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaHPO₄
- Mohs hardness
- 3.5
- Density
- 2.93 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Triclinic
- Crystal habit
- Tabular Crystals, Massive, Granular, Crusts
- Cleavage
- Perfect On {010}
- Rarity
- Rare
- Uses
- Collector, Scientific Research
- Host rock
- Guano Deposits in Limestone Caves
- Typical price
- $20-150 for specimens depending on quality and origin
Where rockhounds find monetite
Classic worldwide localities
- Mona Island, Puerto Rico
- Christmas Island
- Redonda, Antigua and Barbuda
- Sombrero Island
Field-hunting tip
Look in guano deposits in limestone caves country — that is the host setting where monetite typically forms. If you start seeing brushite, hydroxyapatite, whitlockite in float, you are in the right ground. Field specimens usually show a tabular crystals, massive, granular, crusts habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find monetite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
