Perhamite is a rare calcium aluminum silicate mineral often found as crusts or tiny, platy radial aggregates within cavities of granitic pegmatites. It is most famous for its discovery at the Perham Farm in Maine, where it occurs as a secondary mineral resulting from the alteration of other phosphate species. Collectors typically look for its characteristic pale, platy crystal clusters associated with other rare phosphate minerals.
Is this perhamite?
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 perhamite with a known reference. Perhamite sits at Mohs 4 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Perhamite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Perhamite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: colorless, white, gray, pale green.
- 5Look at form & habitCrystal system: trigonal. Typical habit: platy crystals, radial aggregates, massive.
Often confused with
Perhamite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside perhamite
Minerals reported to co-occur with perhamite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₃Al₂(Si₃O₁₂)(OH)₄
- Mohs hardness
- 4
- Density
- 2.44 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Trigonal
- Crystal habit
- Platy Crystals, Radial Aggregates, Massive
- Cleavage
- Perfect Basal
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Granite Pegmatites
- Typical price
- $20-150 thumbnail
Where rockhounds find perhamite
Classic worldwide localities
- Perham Farm, Maine, USA
- Mount Mica, Maine, USA
- Newry, Maine, USA
Field-hunting tip
Look in granite pegmatites country — that is the host setting where perhamite typically forms. If you start seeing eosphorite, lithiophilite, quartz in float, you are in the right ground. Field specimens usually show a platy crystals, radial aggregates, massive habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find perhamite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
