Geological Glossary |

The amphiboles
are a family of silicate minerals that form prism or needle-like crystals.
Amphibole minerals generally contain iron, magnesium, calcium and aluminum
in varying amounts along with silicon, oxygen, and water. Hornblende,
shown in this image, is a common dark green to black variety of amphibole;
it is a component in many igneous and metamorphic rocks. |