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.

Hardness

4-4.5

Mohs

Luster

Satiny on fresh surfaces, dull to earthy

Streak

Pale purple

Transparency

Translucent to opaque

mineraluncommonHeterosite-Purpurite Group family

Heterosite

Hardness: 4-4.5
Luster: Satiny on fresh surfaces, dull to earthy
Streak: Pale purple
Transparency: Translucent to opaque

Is this heterosite?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch heterosite with a known reference. Heterosite sits at Mohs 4-4.5, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: pale purple.
3
Read the luster
Hold the specimen under a strong light. Luster: satiny on fresh surfaces, dull to earthy.
4
Match the color range
Compare against the expected color range: brownish black, violet brown, greenish brown, dark brown, dark pink.
5
Look at form & habit
Crystal 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 pale purple, Triphylite leaves white to grayish white; luster reads satiny on fresh surfaces, dull to earthy on Heterosite and vitreous to subresinous on Triphylite.

Compare →

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.

Triphylite
mineral · Mohs 4-5

All properties

Chemical formula: Fe□PO₄
Mohs hardness: 4-4.5
Density: 3.40 g/cm³
Colors: Brownish blackViolet brownGreenish brown Dark brownDark pink
Streak: Pale purple
Luster: Satiny on fresh surfaces, dull to earthy
Transparency: Translucent to opaque
Crystal system: Orthorhombic
Crystal habit: Massive, granular, or rarely as distinct prismatic crystals
Cleavage: Good on {100}; poor on {010}; surfaces may be curved
Rarity: Uncommon
Uses: Collector, Decorative
Host rock: A secondary mineral in the oxidized zone of complex granite pegmatites, replacing primary phosphate minerals, principally triphylite

Where rockhounds find heterosite

1 mapped spots

Classic worldwide localities

Fletcher and Palermo #1 mines, near North Groton, Grafton Co., New Hampshire, USA
Newry, Oxford Co., Maine, USA
Hill City, Pennington Co., South Dakota, USA
Haute-Vienne, from near Limoges, Huréaux, and in the La Vilate quarry, near Chanteloube, France
Hagendorf, and Hühnerkobel, near Zwiesel, Bavaria, Germany
Norrö pegmatite, on Rånö Island, Sweden

Field-hunting tip

Where it forms: A secondary mineral in the oxidized zone of complex granite pegmatites, replacing primary phosphate minerals, principally triphylite. If you start seeing triphylite, ferrisicklerite in float, you are in the right ground. Typical habit: massive, granular, or rarely as distinct prismatic crystals. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in New Hampshire. Start trip planning there.

Browse 1 U.S. spots for heterosite →

Common questions

How do you identify heterosite?+

Mohs hardness is 4-4.5. Luster: satiny on fresh surfaces, dull to earthy. The streak is pale purple. Common colors include brownish black, violet brown, greenish brown, dark brown.

Where is heterosite found?+

Notable localities include Fletcher and Palermo #1 mines, near North Groton, Grafton Co., New Hampshire, USA; Newry, Oxford Co., Maine, USA; Hill City, Pennington Co., South Dakota, USA; Haute-Vienne, from near Limoges, Huréaux, and in the La Vilate quarry, near Chanteloube, France; Hagendorf, and Hühnerkobel, near Zwiesel, Bavaria, Germany.

Can I find heterosite in the United States?+

RockHoundR maps 1 heterosite rockhounding spots across 1 U.S. states. The top states are New Hampshire.

What rocks look like heterosite?+

Heterosite is most often confused with Purpurite, Triphylite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with heterosite?+

Heterosite commonly co-occurs with Triphylite, Ferrisicklerite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does heterosite form in?+

Where it forms: A secondary mineral in the oxidized zone of complex granite pegmatites, replacing primary phosphate minerals, principally triphylite. Working float back to the host body is the standard way to chase a fresh occurrence.

What is heterosite used for?+

Heterosite is used in collector, decorative.

Find heterosite on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.