Geology 101 - Spring 2010, Sedimentary Rocks

Calcarenite/ Fossiliferous Limestone / Skeletal Limestone
Reacts with HCL
Composed of sand size grains, feels rough
Some larger shells may be seen

Bituminous Coal
Black color, may be sooty or bright
May show layeringBiochemical (Bioclastic) composition

Quartz Sandstone

Sand size grains, feels rough
Made up of mostly quartz, will scratch class
Tends to look fairly homogeneousWell sorted

Chert

Microcrystalline variety of quartz, so it scratches glass
May exhibit conchoidal fractureChemical composition

Breccia

Consists of large, angular grainsPoorly sortedDetrital (Siliciclastic) composition

Micrite / Micritic Limestone

Reacts with HCL.
No visible grains.May break with conchoidal fracture. May contain a few visible fossils.Biochemical (Bioclastic) sediment grains.

Conglomerate

Consists of large, rounded, gravel-sized grains.Poorly sorted grains larger than 2mm.Detrital (Siliciclastic) composition.

Coquina

Reacts with HCL.
Made up of large, gravel sized shell or coral fragments.Biochemical (Bioclastic) composition.

Hematitic Sandstone

Sand sized grains, so it feels rough.
Brown/rust color due to the hematite present.Detrital (siliciclastic) composition.

Rock Salt

Salty Taste.
Visible Crystals.
Brittle.Halite mineral crystals.Chemical composition (sediments of water precipitation.)

Oolitic Limestone

Reacts with HCL.
Comprised of spherical grains that resemble small pearls, called ooids.Chemical composition (sediments of water precipitation.)

Mudstone
Mud sized particles.Detrital (siliciclastic) composition.
Smooth.May appear to split into layers (shale) or crumble into blocks (claystone.)

Chalk

Reacts with HCL.
Very soft.
Has distinct white color.Composed of silty sediments comprised of microscopic shells of calcareous phytoplankton (microfossils.)Biochemical (Bioclastic) composition.

Lignite

Dull, dark brown, brittle rock.Biochemical (Bioclastic) composition.Made of plant fragments and/or charcoal.Clay-sized sediment?

Arkose

Sand sized grains, so it feels rough.
Contains grains of feldspar (pink grains.)Detrital (siliciclastic) composition.