Amphibole group

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.[1]

## References[edit]

1. ↑ http://wrgis.wr.usgs.gov/docs/parks/rxmin/mineral.html#amphibole