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. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: white, colorless, light yellow.
- 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
- Indistinct in three directions
- Rarity
- Rare
- Uses
- Collector, Scientific research
- Host rock
- As coatings and cements resulting from guano-induced phosphatization of sedimentary rocks; a coating on phosphate minerals in granite pegmatite
Where rockhounds find monetite
Classic worldwide localities
- Paoha Island, Mono Lake, Mono Co., California, USA
- Monito (Moneta), Mona, Los Monges, and Aruba Islands, West Indies, Caribbean Sea
- Ascension Island, South Atlantic Ocean
- Boqueirão pegmatite, Parelhas, Rio Grande do Norte, Brazil
- Murra-el-elevyn Cave, Cocklebiddy, Western Australia
- Gunong Keriang Cave and the Niah Great Cave, Sarawak, Malaysia
Field-hunting tip
Where it forms: As coatings and cements resulting from guano-induced phosphatization of sedimentary rocks; a coating on phosphate minerals in granite pegmatite. If you start seeing newberyite, gypsum, whitlockite in float, you are in the right ground. Typical habit: tabular crystals, massive, granular, crusts. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify monetite?+
Where is monetite found?+
What rocks look like monetite?+
What minerals are found with monetite?+
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What is monetite used for?+
Find monetite on the map
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