Crandallite is a phosphate mineral that often forms interesting botryoidal or crusty habit formations. It is commonly found as a secondary mineral in phosphate-rich environments and is frequently associated with wavellite or variscite.
Is this crandallite?
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 crandallite with a known reference. Crandallite sits at Mohs 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, dull to chalky when massive.
- 4Match the color rangeCompare against the expected color range: gray, yellow, yellowish white, light red.
- 5Look at form & habitCrystal system: trigonal. Typical habit: compact, fibrous, massive.
Often confused with
Crandallite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside crandallite
Minerals reported to co-occur with crandallite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaAl₃(PO₄)₂(OH)₅·H₂O
- Mohs hardness
- 5
- Density
- 2.78-3.04 g/cm³
- Streak
- White
- Luster
- Vitreous, dull to chalky when massive
- Transparency
- Translucent
- Crystal system
- Trigonal
- Crystal habit
- Compact, fibrous, massive
- Cleavage
- Perfect on {0001}
- Rarity
- Uncommon
- Uses
- Collector
- Host rock
- In weathered phosphatic aluminous sedimentary rocks and carbonatites
Where rockhounds find crandallite
Classic worldwide localities
- Brooklyn mine, near Silver City, Tintic district, Juab Co., at the Little Green Monster mine, Clay Canyon, about nine km west of Fairfield, and from Amatrice Hill, about 40 km northwest of Fairfield, Utah Co., USA
- Palermo #1 and Fletcher mines, near North Groton, Grafton Co., New Hampshire, USA
- Gore, Frederick Co., Virginia, USA
- Dug Hill, near Avant, Garland Co., Arkansas, USA
- Alto Benedito pegmatite, 15 km west of Picuí, Paraíba, Brazil
- Blaton, Belgium
Field-hunting tip
Where it forms: In weathered phosphatic aluminous sedimentary rocks and carbonatites. If you start seeing fluorapatite, hydroxylherderite, quartz in float, you are in the right ground. Typical habit: compact, fibrous, massive. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify crandallite?+
Where is crandallite found?+
What rocks look like crandallite?+
What minerals are found with crandallite?+
What kind of rock does crandallite form in?+
What is crandallite used for?+
Find crandallite on the map
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