Heterosite is an iron-rich phosphate mineral that typically forms as an alteration product of triphylite in phosphate-bearing pegmatites. It is prized by collectors for its distinct, intense purple to dark red color, though the color often fades or darkens to brown upon long-term exposure to sunlight.
Is this heterosite?
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 heterosite with a known reference. Heterosite sits at Mohs 4-5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Heterosite leaves a light violet to brownish-purple streak.
- 3Read the lusterHold the specimen under a strong light. Heterosite typically shows a dull to sub-metallic luster.
- 4Match the color rangeCompare against the expected color range: purple, violet, dark red, brownish-black.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: massive, granular, or rarely as distinct prismatic crystals.
Often confused with
Heterosite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Heterosite leaves light violet to brownish-purple, Purpurite leaves purple; luster reads dull to sub-metallic on Heterosite and dull on Purpurite.
How to tell apart: Streak differs — Heterosite leaves light violet to brownish-purple, Triphylite leaves white; luster reads dull to sub-metallic on Heterosite and vitreous on Triphylite.
Often found alongside heterosite
Minerals reported to co-occur with heterosite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Fe³⁺,Mn³⁺)PO₄
- Mohs hardness
- 4-5
- Density
- 3.2-3.5 g/cm³
- Streak
- Light Violet to Brownish-purple
- Luster
- Dull to Sub-metallic
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Massive, Granular, Or Rarely as Distinct Prismatic Crystals
- Cleavage
- Good in One Direction
- Rarity
- Uncommon
- Uses
- Collector, Decorative
- Host rock
- Granite Pegmatites
- Typical price
- $10-100 per specimen
Where rockhounds find heterosite
Classic worldwide localities
- France
- USA (Maine, South Dakota)
- Brazil
- Namibia
- Sweden
Field-hunting tip
Look in granite pegmatites country — that is the host setting where heterosite typically forms. If you start seeing triphylite, lithiophilite, quartz in float, you are in the right ground. Field specimens usually show a massive, granular, or rarely as distinct prismatic crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find heterosite on the map
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