Sedimentary Rocks Types and Classification

Detritial or Clastic Derived from the weathering of pre-existing rocks, which have been transported and deposited. Occur in layers sometimes – never wavy

Detritial or Clastic Detritial Rocks are classified by grain size. –Gravel: Grain size greater than 2 mm If rounded clasts = conglomerate If angular clasts = breccia BrecciaConglomerate

Detritial or Clastic Sand: Grain size 1/16 to 2 mm –Sandstone

Detritial or Clastic Silt: Grain size 1/256 to 1/16 mm (gritty) –Siltstone

Detritial or Clastic Clay: Grain size less than 1/256 mm (smooth) –Shale (if fissile – splits easily) –Claystone (if massive)

Chemical or Biochemical These rocks form from chemical components dissolved in the seawater. These chemicals may be removed from seawater and made into rocks by chemical processes, or with the assistance of biological processes (such as shell growth).

Chemical and Biochemical Evaporites form from evaportation of water, usually seawater –Rock Salt – composed of halite (NaCl) –Rock Gypsum – composed of gypsum Salt Flats in Salt Lake City, UT Layered Gypsum, NM Gypsum Crystals, Australia

Chemical and Biochemical 1.Carbonates - The carbonate sedimentary rocks are formed through both chemical and biochemical processes. They include the limestones (many types) and dolostones. 1.Two minerals are dominant in carbonate rocks: 1.Calcite (CaCO 3 ) 2.Dolomite (CaMg(CO 3 ) 2 ) 2.Carbonate rock names: 1.Fossiliferous limestone 2.Coquina 3.Chalk

Chemical and Biochemical Limestone

Organics (Coals) This group consists of rocks composed of organic matter (mainly plant fragments ). Because of this, they lack minerals (which must be inorganic, be definition). These are the coals. In order of increasing depth of burial (temperature and pressure): – Peat – Bituminous – Anthracite

Metamorphic Rocks Types and Classification

Metamorphic Rocks Metamorphic rocks are rocks that have "morphed" into another kind of rock. The rocks are under tons and tons of pressure, which fosters heat build up, and this causes them to change. If you exam metamorphic rock samples closely, you'll discover how flattened some of the grains in the rock are.

How do Rocks Change? Metamorphism causes changes in –Texture Recrystallization –Growth of new crystals –Orientation of crystals - FOLIATION Compaction 1.The grains move closer together. 2.The rock becomes more dense. 3.Porosity is reduced. –Mineralogy – formation of new minerals

Foliated Metamorphic Rocks Alignment of minerals – evident in bands or layers, may be wavy!

Non Foliated Metamorphic No noticable layers Marble Quartzite

Changing Rocks Slate - MetamorphicShale - Sedimentary

Common Metamorphic Rocks ClassificationMetamorphic Rock Parent RockCommon Minerals Foliated (Banded) SlateShale, mudstoneQuartz, clay minerals (feldspars) SchistShale, slate, basalt, or graniteMica, chlorite, talc, quartz GneissShale, schist, granite, sandstone, and other rock types Quartz, feldspars Non-Foliated (Not Banded) QuartziteSandstoneQuartz MarbleLimestone, dolomiteCalcite Anthracite coalBituminous coalCrystalline carbon