Andesite Extrusive igneous rock primarily plagioclase plus pyroxene, hornblende, magnetite, biotite and quartz, equivalent to the plutonic rock diorite.
Basalt An extrusive igneous rock similar to the intrusive igneous rock gabbro. Found in many of the volcanoes of the oceanic islands and also in areas of Oregon, Idaho, Washington in the United States and in India, Siberia and other parts of the world. Contains calcium rich feldspars, olivine and many iron rich minerals.
Dacite Is an extrusive igneous rock with a composition between rhyolite and andesite.
Diorite It is a plutonic igneous rock that contains plagioclase, biotite, hornblende and/or pyroxene.
Gabbro Is a coarse grained plutonic igneous rock with a composition of basalt.
Granite Granite is a plutonic igneous rock with a coarse crystalline texture and is the most common igneous rock. The chemistry is the same as the fine-grained igneous rock rhyolite. Granite can contain quartz, mica, feldspars, hornblende, and several other minerals.
Obsidian This rock is an extrusive rock that cools so fast that crystals do not have a chance to form making it a natural glass.
Pegmatite This is granite that can contain large gemstone size crystals of minerals like; tourmaline, beryl, zircon and others.
Pumice Is an igneous rock that has a porosity that is full of air; it is a felsic rock that is similar to rhyolite.
Rhyolite It is the extrusive equivalent to the intrusive igneous rock granite.
Scoria Scoria is similar to pumice except the lava that it formed from was more viscous containing more rock and less air in the structure.
Tuff Tuff forms explosively as it is ejected from volcanic vents. Tuff samples have several names assigned to them depending on their formation, ash-fall, ash-flow, welded tuff, etc.