Rocks: Igneous, Metamorphic and Sedimentary - Geology.com
Photographs and information for a large collection of igneous, metamorphic and sedimentary rocks. Geology.com.
Igneous Rocks | Pictures of Intrusive and Extrusive Rock Types
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.
Sedimentary Rocks | Pictures, Characteristics, Textures, Types
Organic sedimentary rocks form from the accumulation of plant or animal debris. Examples include: chalk, coal, diatomite, some dolomites, and some limestones. Photos and brief descriptions of some common sedimentary rock types are shown on this page.
Mineral Properties, Photos, Uses and Descriptions - Geology.com
Photos and information about 80 common rock-forming, ore and gemstone minerals from around the world.
Gemstones: Facts, photos, and information for over 100 gems.
Articles about gemstones written by a GIA Graduate Gemologist. Each article includes photos and information about the gem's physical properties and geologic origin.
Metamorphic Rocks | Pictures of Foliated and Non-Foliated Types
Metamorphic rocks have been modified by heat, pressure, and chemical processes, usually while buried deep below Earth's surface. Exposure to these extreme conditions has altered the mineralogy, texture, and chemical composition of the rocks. There are two basic types of metamorphic rocks.
The "Acid Test" for Carbonate Minerals and Carbonate Rocks
Some rocks contain carbonate minerals, and the acid test can be used to help identify them. Limestone is composed almost entirely of calcite and will produce a vigorous fizz with a drop of hydrochloric acid.
Quartzite: Metamorphic Rock - Pictures, Definition & More
Quartzite is a nonfoliated metamorphic rock composed almost entirely of quartz. It forms when a quartz-rich sandstone is altered by the heat, pressure, and chemical activity of metamorphism. Metamorphism recrystallizes the sand grains and the silica cement that binds them together.
Meteorite Identification: Have you found a space rock?
Identification of a genuine meteorite takes a practiced eye, but there are a number of simple tests that can help hopeful rock hounds determine if they have stumbled across a rare space rock, or just a common earthbound stone.
Granite: Igneous Rock - Pictures, Definition & More - Geology.com
Granite is the most widely known igneous rock. It is an intrusive rock with visible grains of feldspar, quartz, mica, and amphibole minerals. It is durable and widely used in construction and architecture.