These samples of hornblende are displayed in the Smithsonian Museum of Natural History. Hornblende is one of the basic silicate minerals. Its composition is Ca2(Mg,Fe,Al)5(Si,Al)8O22(OH)2. Hornblende is the most common example of the group of silicates called amphibole. The sample at left is about 12x8 cm and is from Ontario, Canada.

This sample of hornblende with calcite is from Franklin, New Jersey. It is about 15 cm across.

This sample of hornblende is from Russell, New York. It is about 5 cm wide.

Hornblende has two cleavage directions that intersect at roughly 60° and 120°. It is usually dark green to black in color and is similar to augite. It is commonly found in continental rocks which are igneous in origin. It often makes up the dark part of rocks which are composed of light and dark crystals.

Mindat: Hornblende

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