1. Rock Identification Learn Your Rocks Rock ID Practice Test Click Here to Learn more about a specific rock. Click Here to take a practice Rock ID Test Quartz Sandstone Garnet Mica Schist Obsidian By Marvin Lowe © Lowe Power Graphics

2. Learn Your Rocks Gneiss Obsidian Pumice Slate Mica Schist Conglomerate Garnet Mica Schist Quartz Sandstone Fossillferous Limestone Quartzite Granite Rhyolite Diorite Breccia Shale Basalt Rock Salt Agate Marble Coquina Gabbro Chert Scoria Andisite Chalk Select a rock to learn more about it.

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29. Gneiss A banded or foliated rock usually made from some type of granite. Color will vary considerably based on the amount and kind of minerals found in the original granitic rock. Acid TestNo Reaction Scratch TestWill scratch glass Rock TypeMetamorphic Particle Size, Texture Foliated, Crystalline Mineral Composition Amphibole, Feldspar, Quartz

31. Obsidian Acid TestNo Reaction Scratch TestWill scratch glass Rock TypeIgneous, Extrusive Particle Size, Texture Compact Glassy Mineral Composition Silica Rich A black, banded, or spotted hard volcanic glass that is formed by very rapid cooling of lava. Historically, many different peoples have used the glass rock to fashion sharp tools such as knives and spear points.

33. Pumice Acid TestNo Reaction Scratch TestWill scratch glass Rock TypeIgneous, Extrusive Particle Size, Texture Compact, Fibrous, Glassy Mineral Composition Silica Rich A light, porous, fibrous, glassy lava, used in solid form as an abrasive and in powdered form as a polish and an abrasive. Sometimes it’s density is low enough that it will float in water. Pumice is lava that had a lot of gases in it and cooled quickly on the surface of the earth.

35. Conglomerate Acid TestNo Reaction Scratch TestWill scratch glass Rock TypeSedimentary Particle Size, Texture Gravel and smaller sized particles Mineral Composition Varied, heterogeneous mixture A rock consisting of heterogeneous pebbles and gravel embeded in a cement made of clay, silt and sand particles.

37. Garnet Mica Schist Acid TestNo Reaction Scratch TestWill scratch glass Rock TypeMetamorphic Particle Size, Texture Leaf like foliation Mineral Composition Muscovite and Garnet A mica rich leafed foliated rock that is formed under great heat and pressure. Garnet crystals have developed on the rock as it was being formed. The rock may be silvery white to various shades of grey and exhibit yellow to brown tones depending on the oxidation of the various minerals in the rock sample.

39. Quartz Sandstone Acid TestNo Reaction Scratch TestWill scratch glass Rock TypeSedimentary Particle Size, Texture Sand size, crystalline Mineral Composition Quartz A rock formed by the consolidation and compaction of generally rounded sand particles cemented together by clay, silt, or silica particles. The color will vary based on the trace elements present in the quartz sand particles. The rock may show color banding and cross-bedding patterns.

41. Fossillferous Limestone Acid TestReacts with Acid Scratch TestWill not scratch glass Rock TypeSedimentary Particle Size, Texture Sand size, smooth Mineral Composition Calcite A common sedimentary rock consisting mostly of calcium carbonate which contains fossils of various fresh and or salt water shell fish. It is used as a building stone, and in the manufacture of lime, carbon dioxide, and cement.

43. Quartzite Acid TestNo Reaction Scratch TestWill scratch glass Rock TypeMetamorphic Particle Size, Texture Non-foliated, Crystalline Mineral Composition Quartz A rock formed by the metamorphism of quartz sandstone. Quartz is a very hard mineral composed of silica. Quartzite can be a wide variety of colors depending on what elements are present in small amounts. Quartzite is very prevalent and is found worldwide.

45. Granite Acid TestNo Reaction Scratch TestWill scratch glass Rock TypeIgneous, Intrusive Particle Size, Texture Course grained, Crystalline Mineral Composition Quartz, Potassium Feldspar A common hard igneous rock consisting mostly of quartz, orthoclase or microcline, and mica. Granite is used for building and paving.

47. Rhyolite Acid TestNo Reaction Scratch TestWill scratch glass Rock TypeIgneous, Extrusive Particle Size, Texture Fine grained Mineral Composition Light color indicates a felsic composition A volcanic rock similar to granite in composite that cooled much more rapidly than granite that usually exhibits flow lines. Color may vary.

49. Diorite Acid TestNo Reaction Scratch TestWill scratch glass Rock TypeIgneous, Intrusive Particle Size, Texture Course grained Crystalline Mineral Composition Amphibole, Intermediate Feldspar Any of various intermediate to dark granite textured crystalline rocks rich in plagioclase.

51. Breccia Acid TestNo Reaction Scratch TestWill scratch glass Rock TypeSedimentary Particle Size, Texture Gravel size to smaller angular broken rock Mineral Composition Large variety Rock composed of sharp angled fragments embedded in a fine grained matrix of sand, silt, and clay particles. The sharp edged rock generally are from a talus slope.

53. Shale Acid TestNo Reaction Scratch TestWill not scratch glass Rock TypeSedimentary Particle Size, Texture Clay sized particles Mineral Composition Clay minerals A rock composed of fine grained layers of sediment. Shale is often embedded with Fossils of plant and animal material.

55. Slate Acid TestNo Reaction Scratch TestWill not scratch glass Rock TypeMetamorphic Particle Size, Texture Foliated, fairly smooth Mineral Composition Clay minerals A fine grained, grayish metamorphic rock that splits into smooth surfaced layers. It has been used for blackboards, roofing material and paving stones. It is generally made of metamorphosed shale..

57. Basalt Acid TestNo Reaction Scratch TestWill scratch glass Rock TypeIgneous, Extrusive Particle Size, Texture Fine grained Crystalline Mineral Composition Amphibole, pyroxene Intermediate Feldspar A hard dense igneous rock composed chiefly of plagioclase, pyroxene And olivine and often having a glassy appearance.

59. Rock Salt Acid TestNo Reaction Scratch TestWill not scratch glass Rock Type Chemical Sedimentary, Evaporite Particle Size, Texture Solid mass of inter- grown crystals. Mineral Composition Halite, trace minerals A rock containing mostly halite, table salt, as its main constituent. The color of the rock salt can vary depending on the trace mineral present In the sample. This is an evaporite in that it is the salt left after the salt has evaporated from saltwater. It is very tasty.

61. Agate Acid TestNo Reaction Scratch TestWill scratch glass Rock TypeChemical Sedimentary Particle Size, Texture Micro-crystalline Mineral Composition Quartz, Trace minerals A fine grained variety of quartz with colored banding. The colored banding results from the presence of various trace elements. Agates have been cut and polished to use for jewelry for some time.

63. Marble Acid TestReacts with acid Scratch TestWill scratch glass Rock TypeMetamorphic Particle Size, Texture Non-foliated Crystalline Mineral Composition Calcite, Trace Elements A metamorphic rock formed from limestone or dolomite. Irregular Coloring is often present because of trace elements in the marble. Marble is often used for sculpting and as a building material.

65. Mica Schist Acid TestNo Reaction Scratch TestWill not scratch glass Rock TypeMetamorphic Particle Size, Texture Foliated Mineral Composition Muscovite, Biotite Medium to course grained metamorphic rocks composed of laminated often flaky parallel layers of micaceous rock.

67. Coquina Acid TestReacts with acid Scratch TestWill not scratch glass Rock TypeSedimentary, Organic Particle Size, Texture Gravel size and smaller shell material Mineral Composition Calcite, Calcium Carbonate Cream to pale brown, porous, poorly cemented organic limestone composed of marine or freshwater mollusk shells and shell fragments.

69. Chalk Acid TestReacts with acid Scratch TestWill not scratch glass Rock TypeSedimentary, Organic Particle Size, Texture Fine particles, very soft Mineral Composition Calcium Carbonate, Calcite, Trace minerals A soft compact calcite with varying amounts of quartz, silica, feldspar, and other mineral impurities. Chalk is generally grey-white to yellow- White in color. It is derived chiefly from fossil sea shells.

71. Gabbro Acid TestNo Reaction Scratch TestWill scratch glass Rock TypeIgneous, Intrusive Particle Size, Texture Course grained, Crystalline Mineral Composition Calcic plagioclase, pyroxene A course grained igneous rock composed chiefly of calcic plagioclase and pyroxene

73. Chert Acid TestNo Reaction Scratch TestWill scratch glass Rock TypeSedimentary Particle Size, Texture Dense & smooth Fine Particles Mineral Composition Chalcedonic, opaline silica, color varies A siliceous rock of chalcedonic or opaline silica occurring in limestone. Color may vary considerably. White to grey to black sample will probably be flint. Yellow green brown and red will probably be Jasper.

75. Scoria Acid TestNo Reaction Scratch TestWill scratch glass Rock TypeIgneous, Extrusive Particle Size, Texture Rough grained, fine crystalline Mineral Composition Plagioclase feldspar, pyroxine A volcanic rock having vesicular structure due to the gases that are moving through the lava as it cools and solidifies. Scoria has basaltic composition. It can vary in color from dark grey to black or dark brown to reddish rust.

77. Andesite Acid TestNo Reaction Scratch TestWill scratch glass Rock Type Igneous, Extrusive or Dikes & sills Intrusive Particle Size, Texture Fine grained, Crystalline Mineral Composition Plagioclase, Feldspar, amphibole, Pyroxene, Biotite A A white to grey igneous rock that usually forms on the surface in lava flows (extrusive) or sometimes as dikes and sills (intrusive) under.