Full View

Contents of 3.2 Can rocks be classified according to the processes that form them?

• Rocks can be classified descriptively or genetically. The three classes of rocks are genetic categories.
• Igneous rocks crystallize as intergrown mineral masses from the molten state in extrusive or intrusive fashion.
• Sedimentary rocks derive from weathering of previously existing rocks as particles or dissolved ions. Clastic sed rocks form from the fragments, and chemical sed rocks from the dissolved portion.
• Metamorphic rocks form by the reaction of preexisting rocks in the presence of heat, pressure, fluids, or combinations thereof, producing new minerals and rocks.