Rocks Igneous = formed by the cooling and crystallization of magma (melted rock) Sedimentary = formed from accumulation of weathered material (sediments) Metamorphic = formed from preexisting rocks that have been transformed (changed)
Igneous, Sedimentary, Metamorphic Each type of rock records a different complex past. Each type of rock can be changed from one form to another and back again. geologists call these transformations the “rock cycle”
What are Rocks? What are Minerals? Rocks An aggregate or mixture of minerals. Composition can vary Most rocks are composed of more than one mineral Minerals Inorganic chemical elements or compounds found in the Earth’s crust. > 3000 minerals are found in Earth’s crust
Physical Properties of Minerals Crystal form Hardness Plane of Cleavage Luster Color and Streak Specific Gravity
Mineral Luster the appearance of its surface as it reflects light minerals of the same color can have different luster.
Color and Streak Color: red rubies, or blue sapphires, same mineral—corundum (Al 2 O 3 )Color Streak refers to the color of a mineral in its powdered form, example – hematiteStreak
Specific Gravity A density measure compares weight of a volume of substance to the weight of the same volume of water Example: –cm 3 pyrite weighs 5X as much as cm 3 water – cm 3 gold weighs 20X more than cm 3 water
Igneous Rock formed by cooling & crystallization of magma. means “formed by fire” make up about 95% of the earth’s crust basalt (ocean floor) and granite (continents) are common examples
Igneous Rock Extrusive Form at earth surface Example-basalt Fine texture Small minerals Fast cooling Intrusive Form inside crust Example-granite Course texture Large minerals Slow cooling
Sedimentary Rock formed from the weathered material carried by water, wind, or ice most common rocks in the upper crust cover over 2/3 of the earth’s surface sandstone, shale, and limestone
Sedimentary Rock Clastic Broken pieces of rock Particle deposition at river bottom, beach, or desert Cementation Ex-quartz mineral forms sandstone Chemical Dissolved materials precipitate from solution Inorganic or organic Ex-calcite mineral or calcium carbonate from shells forms limestone
Sedimentary Rocks SedimentSedimentary Rock Gravel and cobblesConglomerate SandSandstone Silt and clayShale Calcium carbonateLimestone Calcium sulfateGypsum Sodium chlorideHalite
Metamorphic Rock ---formed from preexisting rocks (igneous, sedimentary, or other metamorphic) ----metamorphic means “changing in form” ----marble and slate are common examples
Metamorphic Rock Foliated Elongated minerals align in parallel layers H & P separates minerals into parallel layers Igneous granite to metamorphic gneiss Nonfoliated Smooth, solid homogenous blend of minerals in rock H & P recrystallizes rock Igneous limestone to metamorphic marble.
Metamorphic Rock Original RockMetamorphic Rock SandstoneQuartzite LimestoneMarble ShaleSlate, Schist GraniteGneiss