Photographs and information for a large collection of igneous, metamorphic and sedimentary rocks. Geology.com

Photos and information about 80 common rock-forming, ore and gemstone minerals from around the world.

Geology.com is one of the world's leading portals to geology and Earth science news and information for rocks, minerals, gemstones, energy, volcanoes, earthquakes, careers, geologic hazards, and more.

What Are Rock-Forming Minerals? Scientists have identified over 4,000 different minerals. A small group of these minerals make up almost 90% of the rocks of Earth’s crust. These minerals are known as the common rock-forming minerals.

Extrusive igneous rocks erupt onto the surface, where they cool quickly to form small crystals. Some cool so quickly that they form an amorphous glass. These rocks include: andesite, basalt, dacite, obsidian, pumice, rhyolite, scoria, and tuff. Pictures and brief descriptions of some common igneous rock types are shown on this page.

Rocks: Galleries of igneous, sedimentary and metamorphic rock photos with descriptions. Minerals: Information about ore minerals, gem materials and rock-forming minerals. Volcanoes: Articles about volcanoes, volcanic hazards and eruptions past and present.

Minerals: Information about ore minerals, gem materials and rock-forming minerals. Volcanoes: Articles about volcanoes, volcanic hazards and eruptions past and present. Gemstones: Colorful images and articles about diamonds and colored stones.

A small number of minerals and rocks will glow with spectacular colors under ultraviolet light. Learn how this happens.

Aug 27, 2015 · Many different types of rocks have been identified on Mars. Igneous rocks include basalt and scoria. Sedimentary rocks include conglomerate, sandstone and shale.

Rocks: Galleries of igneous, sedimentary and metamorphic rock photos with descriptions. Minerals: Information about ore minerals, gem materials and rock-forming minerals. Volcanoes: Articles about volcanoes, volcanic hazards and eruptions past and present.