SEDIMENTARY SANDSTONE OIL SHALE LIMESTONE FOSSIL LIMESTONE ROCK GYPSUM
Igneous rocks form from cooled molten material If magma crystallizes underground, then the rock is INTRUSIVE If lava cools above ground, then the rock is EXTRUSIVE At one point in Earth’s history, all rock was igneous
GRANITE (intrusive) Large, interlocking crystals Forms from slow crystallization of magma Composition: Quartz Feldspar Mica “Dimension Stone” Hard (resists scratching) Strong (bears much weight) Inert (resists weathering) Polishes brilliantly
GABBRO (intrusive) Course grained Usually dark green “Black Granite” Composition Plagioclase Augite Very little quartz Uses Cemetery markers Counter tops Floor tiles
OBSIDIAN (extrusive) Molten lava cools quickly (extrusive) “Volcanic glass” Composition No minerals Most is at least a few million years old Not found east of the Mississippi Used as a cutting tool
PUMICE (extrusive) Lava cools during flight, forming pores During an explosive volcanic eruption, may rain down from the sky High silica content Uses: Abrasives for cleaners Scouring agents Insulation
SCORIA (extrusive) Often forms as the top of a lava flow cools Many of the same uses as pumice Porous, light Higher basalt content than pumice, giving it a red to black color
These form from existing rocks that are chemically changed by high heat and/or pressure Parent rocks can be igneous, metamorph ic, or sedimentary
SCHIST Intermediate; between phyllite and gneiss Foliated (low-grade) Contains lots of mica, which allows it to split into pieces Garnet mica schist contains small garnet crystals (dark red)
PHYLLITE Well defined foliation Made of mostly fine- grained mica Intermediate; between slate and schist Formed from morphed shales or mudstones Sedimentary layers have been preserved Orange tint indicates presence of iron
TALC SCHIST (SOAPSTONE) Extremely soft Soapy or greasy texture Talc Softest mineral on Earth Used in baby powder Some areas of the San Andreas Fault contain soapstone Limits severity and frequency of earthquakes Alabaster, serpentine
MARBLE Recrystallized limestone or dolemite, hence the white color Composed entirely of one mineral: calcite Often found interbedded with schists, phyllites, gneisses, and granulites If the marble has other colors, it is because of impurities in the original limestone deposit Uses: Buildings, monuments, tab letops
AMPHIBOLITE Parent rocks: Basalt, gabbro, dolemite (sedimentary) Medium to coarse- grained crystals Hornblende and plagioclaste (ex.)
Sedimentary rocks form from pieces and parts of older rocks, plants, skeletons, s hells, or other debris Most of the rock in our area is sedimentary, like sandstone and slate Sedimentary rocks are the only rocks that we find fossils in
LIMESTONE Composed primarily of CaCO3 (calcium carbonate), or calcite Forms underwater, from shells and skeletons of dead sea creatures Fossil rich Common in PA Limestone blocks were used to construct the Great Pyramid of Egypt
SANDSTONE Clastic rock made up of fine grains of sand “glued” together by minerals (usually quartz) Common to beaches, floodplains, de ltas, and deserts Siltstone, mudstone A red tint indicates the presence of clay
OIL SHALE Shale is extremely common in riverbeds, under, and around lakes Forms from the compaction of silt and clay sized particles Black shales contain organic materials that produce oil, natural gas, and coal
ROCK GYPSUM Gypsum is a common mineral that is used in drywall, plaster, and concrete Sulfate mineral (SO4) Forms in caves Satin spar gypsum and alabaster are used in decorative pieces
ROCK ON!And thank you geology.com for all your useful info and pictures!
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