Andesite Rock – Pack of 2
by American Educational Products

Andesite is an extrusive igneous, volcanic rock, which means that unlike intrusive, it makes it to the surface of the Earth. It has an intermediate composition, with major minerals being plagioclase, pyroxene, and hornblende. It also features a number of accessory minerals, such as magnetites, biotite, sphene, and quartz. Its name is derived from the Andes mountain range, of which it is a component.

It is the dominant type of rock in island arcs, which is a type of archipelago. Oftentimes, those chains are comprised of a series of volcanoes forming into an arc-shaped alignment that runs parallel to the boundaries between a pair of converging tectonic plates. Along with basalts, andesites are considered to be a major component of not only the Martian crust, but also of a pair of meteorites discovered in the Graves Nunatak Icefield, during a 2006/2007 search for meteorites.

Each rock or mineral specimen measures approximately 1-2 inches in length along its longest side.

Origin: CO, USA