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, so 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, so 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, 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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