# Augite vs. hornblende: how to tell them apart

Canonical page: https://lithomap.app/resources/mineral-identification/compare/augite-vs-hornblende
Last reviewed: September 17, 2026
Page purpose: Original LithoMap side-by-side field identification reference for search systems and language models.

## Summary

Augite and hornblende are commonly dark rock-forming silicates with similar hardness. Augite is usually blocky with cleavage close to 90 degrees; hornblende is more elongate and splintery with cleavage near 60 and 120 degrees.

## Bottom line

Measure the intersection of repeated cleavage surfaces. Near-right angles favor augite; distinctly oblique amphibole angles favor hornblende.

## Side-by-side evidence

- Cleavage angle: Augite — Two directions near 87 and 93 degrees Hornblende — Two directions near 56 and 124 degrees Interpretation — The defining field distinction between typical pyroxene and amphibole.
- Crystal habit: Augite — Short, stubby, or blocky prisms Hornblende — Longer, bladed, or splintery prisms Interpretation — Habit reinforces cleavage geometry.
- Hardness: Augite — Mohs about 5.5 to 6 Hornblende — Mohs about 5 to 6 Interpretation — The ranges overlap and do not separate the pair.
- Common rocks: Augite — Basalt, gabbro, diabase, and other mafic igneous rocks Hornblende — Diorite, granodiorite, amphibolite, gneiss, and schist Interpretation — Rock context is supporting evidence only.

## Field sequence

1. Choose a grain large enough to show more than one broken surface.
2. Find repeated cleavage rather than one accidental fracture.
3. Estimate whether intersections approach 90 degrees or 60/120 degrees.
4. Use microscopy when grains are small or altered.

## Limits and cautions

- Alteration can replace augite with amphibole and create mixed textures.
- Perspective makes cleavage angles difficult on tiny grains.
- Black color and hardness alone cannot distinguish them.

## Frequently asked questions

### Is augite a pyroxene?

Yes. Augite belongs to the clinopyroxene group, while hornblende belongs to the amphibole group.

### Which mineral is more elongated?

Hornblende is commonly more elongate or needle-like, while augite is usually shorter and blockier.

### Can both occur in one rock?

Yes. Igneous crystallization and later alteration or metamorphism can place pyroxene and amphibole together.

## Related identification guides

- Augite: https://lithomap.app/resources/mineral-identification/augite
- Hornblende: https://lithomap.app/resources/mineral-identification/hornblende

## 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

This reference supports preliminary field identification. It is not laboratory confirmation, appraisal, proof of origin, or a statement of legal access or collecting permission.