A to Z Rocks

So I'm going to start out something fun. I'm going to list off rock specimens A through Z. Either going to try to get one in for each day or more than one a day. There are three different types of rock: Igneous, Sedimentary, and metamorphic rocks.

I'm going to start with the letter A of this specimen, Andesite.

Andesite is a fine-grained, extrusive igneous rock composed mostly of plagioclase with other minerals such as hornblende, pyroxene and biotite.