Augite is a silicate with composition (Ca, Mg,Fe)2(Si,Al)2O6. This sample is about 9 cm across cm and is from Sterling Hill mine, Ogdensburg, New Jersey. These samples are on display at the Smithsonian Museum of Natural History.
Augite is a basic silicate mineral with high content of iron and magnesium, a so-called "ferromagnesian" mineral of the pyroxene grouping. This identifies it as a high-crystallization-temperature dark silicate, formed at early stages of the Bowen reaction series.
Augite is often found as crystals in basalt.