SEDIMENTARY ROCK SPECIMEN
Rocks are simply defined as an aggregate of minerals. There three classifications Igneous Rocks formed from cooled lava and magma associated with volcanic activity. Sedimentary Rocks formed from compacting sediments (pebbles, sand and clay) often below sea level. Metamorphic Rocks forms from preexisting rocks that get buried and remain in a solid state while immersed at various levels of heat and pressure.
Sedimentary Rocks
Detrital sediments result from the erosion and subsequent transportation of a pre-existing rock; chemiscal sediments form by primary precipitation in shallow marine environments; organic sediments form from biological activity.
Sedimentary Rocks: Clastic from detrital inorganic matteral
Rock name: Breccia (Italian meaning: “broken stone” or “rubble”).
Rock type: Sedimentary.
Rock classification: Clastic.
Origin/Environment: Techtonics-Breccia may originate as a result of talus accumulation, explosive igneous processes, collapse of rock material, or faulting.
Description: A coarse-grained clastic rock, composed of angular broken rock fragments held together by a mineral cement or in a fine-grained matrix; it differs from conglomerate in that the fragments have sharp edges and unworn corners.
Rock name: Breccia (Italian meaning: “broken stone” or “rubble”).
Rock type: Sedimentary.
Rock classification: Clastic.
Origin/Environment: Techtonics-Breccia may originate as a result of talus accumulation, explosive igneous processes, collapse of rock material, or faulting.
Description: A coarse-grained clastic rock, composed of angular broken rock fragments held together by a mineral cement or in a fine-grained matrix; it differs from conglomerate in that the fragments have sharp edges and unworn corners.
Rock name: Breccia (Italian meaning: “broken stone” or “rubble”).
Rock type: Sedimentary.
Rock classification: Clastic.
Origin/Environment: Techtonics-Breccia may originate as a result of talus accumulation, explosive igneous processes, collapse of rock material, or faulting.
Description: A coarse-grained clastic rock, composed of angular broken rock fragments held together by a mineral cement or in a fine-grained matrix; it differs from conglomerate in that the fragments have sharp edges and unworn corners.
Rock name: Conglomerate.
Rock type: Sedimentary.
Rock classification: Clastic.
Origin/Environment: Rounded and smoothed from transportation by water or from wave action.
Description: Coarse-grains composed of >25% rounded to subangular clast or rock fragments larger than 2 mm in diameter (granules, pebbles, cobbles, boulders) set in a fine-grained matrix of sand or silt, and commonly cemented by calcium carbonate, iron oxide, silica, or hardened clay; the consolidated equivalent of gravel.
Rock name: Conglomerate.
Rock type: Sedimentary.
Rock classification: Clastic.
Origin/Environment: Rounded and smoothed from transportation by water or from wave action.
Description: Coarse-grains composed of >25% rounded to subangular clast or rock fragments larger than 2 mm in diameter (granules, pebbles, cobbles, boulders) set in a fine-grained matrix of sand or silt, and commonly cemented by calcium carbonate, iron oxide, silica, or hardened clay; the consolidated equivalent of gravel.
Rock name: Sandstone.
Rock type: Sedimentary.
Rock classification: Clastic.
Origin/Environment: I collected this specimen eight miles north of Llano, Texas. Formed in a prehistoric river stream.
Description: A medium-grained clast of fragments of sand size (0.1-2mm diameter) set in a fine-grained matrix (silt or clay) firmly united by a cementing material (commonly silica, iron oxide, or calcium carbonate) about 80% quartz.
Rock name: Sandstone.
Rock type: Sedimentary.
Rock classification: Clastic.
Origin/Environment: I collected this specimen in early Permain deposits in Seymour, Texas.
Description: A medium-grained clast of fragments of sand size (0.1-2mm diameter) set in a fine-grained matrix (silt or clay) firmly united by a cementing material (commonly silica, iron oxide, or calcium carbonate) about 80% quartz.
Rock name: Shale and Sandstone (Varves).
Rock type: Sedimentary.
Rock classification: Clastic.
Origin/Environment: Deposition of thin Sandstone and Sahle over repeating annual cycles.
Description: Thin gray and tan layers that are characterized by finely laminated structure parallel to the bedding.
Rock name: Shale.
Rock type: Sedimentary.
Rock classification: Clastic.
Origin/Environment: Layed clay that deposits in swamps, littoral (tidal flats), and deep ocean environments.
Description: A fine-grained detrital sedimentary rock, formed by the consolidation/compression of clay, silt, or mud. It is characterized by finely laminated structure parallel to the bedding.
Rock name: Fossiliferous Shale.
Rock type: Sedimentary.
Rock classification: Clastic.
Origin/Environment: Mud and clay deposits in terrestial (land) swamps and lakes.
Description: A layers gray rock with black plant fossils.
Rock name: Fossiliferous Shale – Stone City Formation.
Rock type: Sedimentary.
Rock classification: Clastic.
Origin/Environment: Mud and clay deposits in Eocene Epoch. Collected in Bryan, Texas.
Description: A layers gray rock with Gastropod (snails) and Bivalve (clams) fossils.
Rock name: Fossiliferous Shale.
Rock type: Sedimentary.
Rock classification: Clastic.
Origin/Environment: Mud and clay deposits in terrestial (land) swamps.
Description: A layers black rock with white Carboniferous plant fossils.
Sedimentary Rocks: Chemical and Bio-Chemical from percipitation
Rock name: Fossiliferous and Petroliferous Limestone.
Rock type: Sedimentary.
Rock classification: Chemical-carbonate rock.
Composition: Calcium carbonate, CaCO3.
Origin/Environment: Depositing in sublittoral (shallow marine) environments. This rock was Collected in Uvalde, Texas in an asphalt mine.
Fossils present: Cretaceous Gastopods (snails)
Description: Tan to white fine-grained rock.
Rock name: Fossiliferous Limestone.
Rock type: Sedimentary.
Rock classification: Chemical-carbonate rock.
Composition: Calcium carbonate, CaCO3.
Origin/Environment: Depositing in sublittoral (shallow marine) environments.
Fossils present: Paleozoic Brachiopods.
Description: Tan to white fine-grained rock with prehistoric shells.
Rock name: Fossiliferous Limestone.
Rock type: Sedimentary.
Rock classification: Chemical-carbonate rock.
Composition: Calcium carbonate, CaCO3.
Origin/Environment: Depositing in sublittoral (shallow marine) environments.
Fossils present: Paleozoic Crinoids.
Description: Tan to white fine-grained rock with prehistoric shells.
Rock name: Travertine Limestone.
Rock type: Sedimentary.
Rock classification: Chemical-carbonate rock.
Composition: Calcium carbonate, CaCO3.
Origin/Environment: Depositing in sublittoral (shallow marine) environments. Then a second diogenetic process with acid in groundwater making holes. This was collected at a gypsum quarry north of Fredericksburg, Texas.
Description: Tan to white fine-grained rock, with near parallel holes.
Rock name: Travertine Limestone (cut and polished).
Rock type: Sedimentary.
Rock classification: Chemical-carbonate rock.
Composition: Calcium carbonate, CaCO3.
Origin/Environment: Depositing in sublittoral (shallow marine) environments. Then a second diogenetic process with acid in groundwater making holes.
Description: Tan to white fine-grained rock, with near parallel holes.
Rock name: Travertine Limestone.
Rock type: Sedimentary.
Rock classification: Chemical-carbonate rock.
Composition: Calcium carbonate, CaCO3.
Origin/Environment: Depositing in sublittoral (shallow marine) environments. Then a second diogenetic process with acid in groundwater making holes.
Description: Tan to white fine-grained rock, with near parallel holes.
Rock name: Limestone with Calcite vein.
Rock type: Sedimentary.
Rock classification: Chemical-carbonate rock.
Composition: Calcium carbonate, CaCO3.
Origin/Environment: Depositing in sublittoral (shallow marine) environments.
Description: Tan to white fine-grained rock.
Rock name: Limestone with layers.
Rock type: Sedimentary.
Rock classification: Chemical-carbonate rock.
Composition: Calcium carbonate, CaCO3.
Origin/Environment: Depositing in sublittoral (shallow marine) environments.
Description: Tan to white fine-grained rock.
Rock name: Dolostone.
Rock type: Sedimentary.
Rock classification: Chemical-carbonate rock.
Composition: CaMg(CO3)2.
Origin/Environment: Depositing in sublittoral (shallow marine) environments. Followed by diagenetic secondary formation.
Description: Tan to white fine-grained rock, denser than Limestone.
Dolostone
Rock name: Bauxite.
Rock type: Sedimentary.
Rock classification: Chemical.
Composition: Varies
Origin/Environment: An aluminum rich clay.
Rock name: Oolitic Limestone.
Rock type: Sedimentary.
Rock classification: Chemical.
Composition: Calcium carbonate, CaCO3.
Origin/Environment: Osiliating lagoonal waters.
Description: Limestone with small spheres.
Rock name: Pisolitic Limestone.
Rock type: Sedimentary.
Rock classification: Chemical.
Composition: Calcium carbonate, CaCO3.
Origin/Environment: Osiliating lagoonal waters.
Description: Limestone with small spheres larger than Oolites.
Rock name: Rock Salt.
Rock type: Sedimentary.
Rock classification: Chemical.
Composition: Sodium chloride, NaCl.
Origin/Environment: Evaporating Sea waters, member of the evaporite sequence.
Description: Translucent rock with cubic angles.
Rock name: Rock Gypsum.
Rock type: Sedimentary.
Rock classification: Chemical.
Composition: Gypsum, CaSO4·2H2O.
Origin/Environment: Evaporating Sea waters, member of the evaporite sequence.
Description: White rocks with visble crystals.
Rock name: Castile Gypsum and Limestone.
Rock type: Sedimentary.
Rock classification: Chemical.
Composition: Gypsum (white) CaSO4·2H2O Limestone (brown) CaCO3.
Origin/Environment: Gypsum is a member of the evaporite sequence. The Castile was collected from a road cut in southeast New Mexico.
Description: A layered white rocks with thin brown intermittent layers.
Sedimentary Rocks: Organic from the remains of living things
Rock name: Coquina.
Rock type: Sedimentary.
Rock classification: Organic.
Composition: Calcium carbonate, CaCO3.
Origin/Environment: Forms in littoral (beach to tidal zone).
Description: Modern shells compacted and cemented together by caliche.
Rock name: Chalk.
Rock type: Sedimentary.
Rock classification: Organic.
Composition: Calcium carbonate, CaCO3.
Origin/Environment: Forms in sublittoral (shallow marine) environments from calcium rich microshells.
Description: White fine-grained limestone.
Rock name: Diatomite.
Rock type: Sedimentary.
Rock classification: Organic.
Composition: Silican dioxide, SiO2.
Origin/Environment: Forms in sublittoral (shallow marine) environments from silica rich microshells.
Description: White fine-grained low density rock.
Rock name: Bituminous Coal.
Rock type: Sedimentary.
Rock classification: Organic.
Origin/Environment: Compacted wood from prehistoric forest.
Description: Black low density mass.
Rock name: Cannel Coal.
Rock type: Sedimentary.
Rock classification: Organic.
Origin/Environment: Compacted wood from prehistoric forest.
Description: Black low density mass.
Rock name: Coal.
Rock type: Sedimentary.
Rock classification: Organic.
Origin/Environment: Compacted wood from prehistoric forest.
Description: Black low-density mass.
Rock name: Flint.
Rock type: Sedimentary.
Rock classification: Bio-chemical.
Origin/Environment: Compacted microshells from plankton and sponges. Collected in gypsum quarry north of Fredericksburg, Texas.
Description: Fine grained silica rich.
Rock name: Novaculite.
Rock type: Sedimentary.
Rock classification: Bio-chemical.
Origin/Environment: Compacted microshells from plankton and sponges. Collected from West Texas road cut.
Description: Fine grained silica rich.
Rock name: Chert.
Rock type: Sedimentary.
Rock classification: Bio-chemical.
Origin/Environment: Compacted microshells from plankton and sponges. Collected in gypsum quarry north of Fredericksburg, Texas.
Description: Fine grained silica rich.
Data: Pellant, Chris. Smithsonian Handbooks. Rocks and Minerals: The clearest recognition guide available. A Dorling Kindersley Book.