Rocks and the Rock Cycle

Rocks are classified into three main types: Igneous, Sedimentary, and Metamorphic.

The types are further categorized based on characteristics associated with their formation.

Igneous Formed from magma Melting and cooling	Sedimentary Formed from sediments Weathering and erosion	Metamormphic Formed from other rocks Heat and Pressure
Extrusive- magma cools quickly at the surface, small crystals Basalt, pumice, obsidian	Clastic- appears to be made of sediments Sandstone, conglomerates, shale	Foliated- visible layers Slate, gneiss
Intrusive- magma cools slowly between layers of rock Diabase, granite	Organic- biotic origin Limestone (from shells), bituminous coal, chalk	Nonfoliated- layers not visible Marble
	Chemical- formed from precipitates Limestone