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Scheme for Sedimentary Rock Identification INORGANIC LAND-DERIVED SEDIMENTARY ROCKS TEXTURE GRAIN SIZE COMPOSITION Pebbles, cobbles, and/or boulders embedded in sand, silt, and/or clay Clastic (fragmental) COMMENTS Rounded fragments Mostly quartz, feldspar, and clay minerals; may contain fragments of other rocks and minerals Sand (0.006 to 0.2 cm) Silt (0.0004 to 0.006 cm) Clay (less than 0.0004 cm) Angular fragments ROCK NAME MAP SYMBOL Conglomerate Breccia Fine to coarse Sandstone Very fine grain Siltstone Compact; may split easily . . . . . . . . . . . . . . . . . . Shale CHEMICALLY AND/OR ORGANICALLY FORMED SEDIMENTARY ROCKS TEXTURE GRAIN SIZE Crystalline Fine to coarse crystals COMPOSITION COMMENTS Halite Gypsum Microscopic to very coarse Bioclastic MAP SYMBOL Rock salt Crystals from chemical precipitates and evaporites Rock gypsum Dolostone Dolomite Crystalline or bioclastic ROCK NAME Calcite Precipitates of biologic origin or cemented shell fragments Carbon Compacted plant remains Limestone Bituminous coal Scheme for Metamorphic Rock Identification TEXTURE GRAIN SIZE COMPOSITION TYPE OF METAMORPHISM Medium to coarse AMPHIBOLE GARNET PYROXENE Fine to medium Regional (Heat and pressure increases) MICA QUARTZ FELDSPAR MINERAL ALIGNMENT NONFOLIATED BANDING FOLIATED Fine Fine Carbon Regional Fine Various minerals Contact (heat) Quartz Fine to coarse COMMENTS ROCK NAME Low-grade metamorphism of shale Slate Foliation surfaces shiny from microscopic mica crystals Phyllite Platy mica crystals visible from metamorphism of clay or feldspars Schist High-grade metamorphism; mineral types segregated into bands Gneiss Metamorphism of bituminous coal MAP SYMBOL Anthracite coal Various rocks changed by heat from nearby magma/lava Hornfels Metamorphism of quartz sandstone Quartzite Regional Calcite and/or dolomite or Metamorphism of limestone or dolostone Marble contact Coarse Various minerals Pebbles may be distorted or stretched Metaconglomerate Source: The University of the State of New York, 2011. Reference Tables for Physical Setting/EARTH SCIENCE. URL: http://www.p12.nysed.gov/assessment/reftable/earthscience-rt/esrt2011-engr.pdf Physical Setting/Earth Science Reference Tables — 2011 Edition 7
