Hornblende

A common black amphibole and the dark specks in many granites and diorites.

Hornblende specimen — Photo: Shannon Heinle, CC0, via Wikimedia Commons

How to identify hornblende

Black to dark green elongated prisms.
Two cleavages meeting at about 56° and 124°.
Shiny, splintery breaks.

Often confused with

Augite
Augite is stubbier with cleavages at nearly 90°.
Compare side by side
Tourmaline
Tourmaline has no cleavage and a triangular cross-section.
Compare side by side
Biotite
Biotite peels into flexible sheets.
Compare side by side

Where it's found

Granites and diorites worldwide
Amphibolites
Ontario, Canada

Uses

Construction stone as a part of rocks.

Rock tumbling

Can be tumbled with care.

Did you know?

The name comes from old German miners' terms meaning 'horn' and 'deceive'.

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