Minerals & Rocks

Minerals & Rocks Mineral - A mineral is a naturally occuring, inorganic, crytalline solid, that has a definite chemical composition, and is stable over a range of temperatures and pressures. Example - Quartz is a mineral, it is found in nature, it forms without the help of plants and animals, it is crystalline, and it has a definite chemical composition (SiO2, two oxygen atoms for every one silicon atom). It is stable, both at low and high temperatures, but is unstable at very high temperatures ( > 600 C). It is stable at low to moderate pressures and is unstable at high pressures (equivalent to burial many tens of kilometers deep). Another common mineral is feldspar . Rock - A rock is an aggregate (a combination) of one or more minerals. It may be igneous, sedimentary or metamorphic. Example - A mixture of crytals of quartz and feldspar is a rock called granite. Granite may also have other minerals such as micas, pyroxene, and amphiboles in lesser amounts, as well as many others in trace quantities. Although there are over 4000 different minerals and hundreds of rock types, there are only about 8 common minerals and 20 common rocks found at the Earth's surface. This makes it relatively easy to learn how to recognize the vast majority of minerals & rocks that you will ever see. All it takes is a little practice.

The most common minerals quartz potassium feldspar plagioclase feldspar

olivine pyroxene amphibole mica calcite

The most common igneous rocks rhyolite granite andesite diorite basalt gabbro peridotite obsidian pumice scoria

The most common sedimentary rocks shale sandstone conglomerate limestone tillite

The most common metamorphic rocks slate phyllite schist gneiss marble quartzite