Pigeonite is a calcium-poor clinopyroxene that is characteristic of rapidly cooled mafic igneous rocks. It is most easily identified in thin section due to its unique optical properties, though in hand samples, it typically appears as brownish-green to black massive grains within basaltic or diabasic matrices.
Is this pigeonite?
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 pigeonite with a known reference. Pigeonite sits at Mohs 6, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: gray white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: brown, greenish brown, light purple brown, black.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic crystals, massive, granular.
Often confused with
Pigeonite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Pigeonite leaves gray white, Augite leaves gray-green.
How to tell apart: Streak differs, so Pigeonite leaves gray white, Enstatite leaves white to grayish.
How to tell apart: Streak differs, so Pigeonite leaves gray white, Diopside leaves white, gray, gray-green.
Often found alongside pigeonite
Minerals reported to co-occur with pigeonite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Ca,Mg,Fe)₂(Mg,Fe)Si₂O₆
- Mohs hardness
- 6
- Density
- 3.17-3.46 g/cm³
- Colors
- Streak
- Gray white
- Luster
- Vitreous
- Transparency
- Semitransparent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic crystals, massive, granular
- Cleavage
- Good on {110}, (110) ^ (110) ~87°; partings on {100}, {010}, and {001}
- Rarity
- Common
- Uses
- Collector, Scientific research
- Host rock
- Common in rapidly cooled siliceous volcanic rocks
Where rockhounds find pigeonite
Classic worldwide localities
- Pigeon Point, Cook Co., Minnesota, USA
- Goose Creek quarry, Leesburg, Loudoun Co., Virginia, USA
- Cobalt area, Ontario, Canada
- Skaergaard intrusion, Kangerdlugssuaq Fjord, Greenland
- Bushveld complex, Transvaal, South Africa
- Hakone volcano, Iwate Prefecture, Japan
Field-hunting tip
Where it forms: Common in rapidly cooled siliceous volcanic rocks. If you start seeing augite, olivine in float, you are in the right ground. Typical habit: prismatic crystals, massive, granular. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify pigeonite?+
Where is pigeonite found?+
What rocks look like pigeonite?+
What minerals are found with pigeonite?+
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Find pigeonite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
