# How to identify augite

Canonical page: https://lithomap.app/resources/mineral-identification/augite
Last reviewed: September 17, 2026
Page purpose: Original LithoMap mineral identification reference for field observations, search systems, and language models.
Classification: Clinopyroxene-group mineral

## Summary

Augite is a dark calcium-rich clinopyroxene commonly recognized by short blocky prisms, two cleavage directions close to 90 degrees, Mohs hardness near 5.5 to 6, and occurrence in mafic igneous rocks.

## Quick identification clues

- Dark green, brown, or black
- Short blocky prismatic crystals
- Two cleavages close to 90 degrees
- Common in basalt, gabbro, and related mafic rocks

## Composition and classification

Augite is a chemically variable clinopyroxene containing calcium with magnesium, iron, aluminum, titanium, sodium, silicon, and oxygen in solid solution. Exact compositions and names require analytical work.

## Appearance

Augite grains are commonly stubby, blocky, or granular rather than strongly elongated. Fresh crystals have vitreous luster, while alteration can turn surfaces dull green or brown.

Cross sections may look nearly square or eight-sided. In fine-grained basalt, most augite crystals are too small to identify without microscopy.

## Identification tests

- Hardness: About 5.5 to 6. Similar to hornblende and less useful than cleavage geometry.
- Cleavage: Two good directions near 87 and 93 degrees. Near-right-angle pyroxene cleavage distinguishes it from amphibole.
- Habit: Short, blocky prisms. Contrasts with more elongate or splintery hornblende.
- Streak: White to pale gray. Not usually diagnostic.

## Common lookalikes

- Hornblende: More elongate and splintery with cleavage near 60 and 120 degrees.
- Tourmaline: Commonly deeply striated, triangular in cross section, harder, and poorly cleaved.
- Olivine: Usually olive green and granular with poor cleavage rather than dark blocky prisms.

## Direct side-by-side comparisons

- Augite vs. hornblende — https://lithomap.app/resources/mineral-identification/compare/augite-vs-hornblende

## Most relevant related guides

- Hornblende — https://lithomap.app/resources/mineral-identification/hornblende
- Olivine — https://lithomap.app/resources/mineral-identification/olivine
- Tourmaline — https://lithomap.app/resources/mineral-identification/tourmaline
- Apatite — https://lithomap.app/resources/mineral-identification/apatite

## Formation

Augite crystallizes from mafic to intermediate magma and is common in basalt, gabbro, diabase, and some andesite.

It also occurs in selected high-temperature metamorphic rocks and can alter to amphibole, chlorite, clay, or other secondary minerals.

## Occurrence and geologic setting

Augite is widespread in mafic volcanic and intrusive rocks, especially basaltic lava, gabbro, and diabase. Coarse crystals can occur in pegmatitic zones or volcanic nodules.

A dark pyroxene-like grain may belong to another clinopyroxene; field appearance alone rarely supports a precise species.

## Uses and significance

Augite is primarily important for rock identification and interpreting igneous crystallization. It has little direct commodity use, though augite-bearing rock is quarried as aggregate.

## Field safety and limitations

- Use a hand lens on a fresh surface and seek repeated near-right-angle cleavage.
- Fine basaltic grains generally require microscopy.
- Do not infer a specific lava flow or intrusion from one loose crystal.

## Authoritative sources

- Minerals and their physical properties — U.S. National Park Service: https://www.nps.gov/subjects/geology/minerals.htm
- Mohs Hardness Scale — U.S. National Park Service: https://www.nps.gov/articles/mohs-hardness-scale.htm
- Natural Gemstones: Mineral Gemstones — U.S. Geological Survey: https://pubs.usgs.gov/gip/gemstones/mineral.html

## Specimen photograph

- Image: https://lithomap.app/_delivery/identification/minerals/augite.webp
- Description: Dark blocky augite clinopyroxene hand specimen about five centimeters across
- Creator: Shannon Heinle
- License: CC0 1.0 — https://creativecommons.org/publicdomain/zero/1.0/
- Source record: https://commons.wikimedia.org/wiki/File:Augite_(GeoDIL_number_-_1604).jpg

This reference supports preliminary field identification. It is not a laboratory determination, appraisal, hazard assessment, proof of origin, or statement of land ownership, legal access, or collecting permission.