Augite is a primary rock-forming mineral found in a wide variety of mafic and intermediate igneous rocks. It typically appears as dull, dark, stubby prismatic crystals that often exhibit a characteristic blocky fracture. Collectors look for its distinctive near-90-degree cleavage angles, which help distinguish it from the more elongated, splintery appearance of hornblende.
Is this augite?
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 augite with a known reference. Augite sits at Mohs 5.5-6 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Augite leaves a grayish white streak.
- 3Read the lusterHold the specimen under a strong light. Augite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: black, dark green, brownish green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: stubby prismatic crystals, granular, massive.
Often confused with
Augite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Augite leaves grayish white, Hornblende leaves grayish-white.
How to tell apart: Streak differs — Augite leaves grayish white, Aegirine leaves yellowish-grey.
How to tell apart: Streak differs — Augite leaves grayish white, Diopside leaves white.
Often found alongside augite
Minerals reported to co-occur with augite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Ca,Na)(Mg,Fe,Al,Ti)(Si,Al)₂O₆
- Mohs hardness
- 5.5-6
- Density
- 3.2-3.6 g/cm³
- Streak
- Grayish White
- Luster
- Vitreous
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Stubby Prismatic Crystals, Granular, Massive
- Cleavage
- Good in Two Directions At Nearly 90 Degrees
- Rarity
- Common
- Uses
- Collector, Petrological Studies
- Host rock
- Mafic Igneous Rocks Like Basalt, Gabbro, And Andesite
- Typical price
- $5-30 for typical mineral specimens
Where rockhounds find augite
9 mapped spotsClassic worldwide localities
- Vesuvius, Italy
- Eifel Mountains, Germany
- Kola Peninsula, Russia
- Ontario, Canada
- New York, USA
Field-hunting tip
Look in mafic igneous rocks like basalt, gabbro, and andesite country — that is the host setting where augite typically forms. If you start seeing labradorite, olivine, magnetite in float, you are in the right ground. Field specimens usually show a stubby prismatic crystals, granular, massive habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Utah, New Jersey, New Mexico — start trip planning there.
Common questions
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Find augite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
