LithoMap

Mineral identification comparison

Augite vs. hornblende: how to tell them apart

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.

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Dark blocky augite clinopyroxene hand specimen about five centimeters across
AugiteClinopyroxene-group mineralPhoto: Shannon Heinle · CC0 1.0
Dark hornblende amphibole hand specimen about four centimeters across from near Kragerø, Norway
HornblendeAmphibole-group mineralPhoto: Shannon Heinle · CC0 1.0
Quick answer

The most useful distinction

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

Side-by-side evidence

Augite and Hornblende comparison table

PropertyAugiteHornblendeHow to use it
Cleavage angleTwo directions near 87 and 93 degreesTwo directions near 56 and 124 degreesThe defining field distinction between typical pyroxene and amphibole.
Crystal habitShort, stubby, or blocky prismsLonger, bladed, or splintery prismsHabit reinforces cleavage geometry.
HardnessMohs about 5.5 to 6Mohs about 5 to 6The ranges overlap and do not separate the pair.
Common rocksBasalt, gabbro, diabase, and other mafic igneous rocksDiorite, granodiorite, amphibolite, gneiss, and schistRock context is supporting evidence only.
Field sequence

A practical identification sequence

  1. 1

    Choose a grain large enough to show more than one broken surface.

  2. 2

    Find repeated cleavage rather than one accidental fracture.

  3. 3

    Estimate whether intersections approach 90 degrees or 60/120 degrees.

  4. 4

    Use microscopy when grains are small or altered.

Limits and cautions

Where the distinction gets difficult

  • 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.

Use several independent observations. This comparison supports preliminary field identification, not laboratory confirmation, appraisal, proof of origin, or collecting permission.

Common questions

Augite vs. hornblende FAQ

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.

Source basis

Authoritative sources

LithoMap wrote this comparison in original language from the physical properties and geological concepts supported by these public scientific references.

Editorial review: September 17, 2026.

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