ROCKS AND MINERALS

ROCKS: The Building Blocks of LithosphereTHERE ARE THREE TYPES OF ROCKS. THEY ARE: Rocks are made up of one or more minerals. 1. Igneous Rocks : Formed from the cooling of molten rock. A. Extrusive (Volcanic) igneous rocks formed from molten rock that cooled quickly on or near the earth's surface.

B.Intrusive (Plutonic) igneous rocks are the result of the slow cooling of molten rock far beneath the surface.

2. Sedimentary Rocks : Formed in layers as the result of moderate pressure on accumulated sediments.

3. Metamorphic Rocks : Formed from older "parent" rock (either igneous or sedimentary) under intense heat and/or pressure at considerable depths beneath the earth's surface.

Igneous RockIgneous rock forms when magma cools and makes crystals. Magma is a hot liquid made of melted minerals. The minerals can form crystals when they cool. Igneous rock can form underground, where the magma cools slowly. Or, igneous rock can form above ground, where the magma cools quickly. Kinds of Igneous RocksIntrusive (plutonic) formed when magma that crystallized at some depth.Extrusive (volcanic and pyroclastic rocks) formed when molten material reached the earths surface (LAVA) and crystallize. In general, extrusive rocks have a finer grained texture than intrusive rocks. IGNEOUS ROCK GRANITEDIORITEGABBROPERIDOTITE RHYOLITEANDESITEBASALTKOMATIITE OBSIDIANPUMICEVOLCANIC AGGLOMERATEPEGMATITE

Sedimentary rocksSedimentary rocks form from pre-existing rock particles - igneous, metamorphic or sedimentary. The Parent rock undergoes WEATHERING by chemical and/or physical mechanisms into smaller particles. These particles are TRANSPORTED by ice, air or water to a region of lower energy called a sedimentary basin. DEPOSITION takes place as a result of a lowering of hydraulic energy, organic biochemical activity or chemical changes (e.g., solubility). Once deposited, the sediments are LITHIFIED (turned into rock) through COMPACTION (decrease in rock volume due to weight of overlying sediment) and CEMENTATION (chemical precipitation in pore spaces between grains which "glues" the rock together. The primary mineralogical and textural characteristics of the rock can be modified as the sediments are buried deeper in the earth's crust and undergo an increase in both temperature and pressure. These low pressure, low temperature changes are termed DIAGENESISDetrital sedimentary rocksDetrital sedimentary rocks are those for which the material has been transported as solid particles. The particles themselves may have derived from either physical weathering or chemical weathering. The texture of sedimentary rocks is described as "clastic", meaning that they are composed of discrete particles that are compacted and cemented together. An example of a non-clastic texture would be crystalline material. Detrital Sedimentary RocksSediment nameand particle sizeDescriptionRock NameGravel (>2 mm)Rounded rock fragmentsConglomerateAngular rock fragmentsBreciaSand (1/16 to 2 mm)Quartz predominatesQuartz sandstoneQuartz with considerable feldsparArkoseDark color, quartz with considerable feldspar, clay and rocky fragmentsGraywackeMud (