Geology 101 - Spring 2010, Sedimentary Rocks

Bituminous coal is known for its specific characteristics which differentiate it from other types of coal. The correct answer describes the typical characteristics of bituminous coal, while the incorrect answers highlight characteristics that are not associated with bituminous coal but with other types of coal or geological compositions.

Chert is specifically a type of silica composed of microcrystalline quartz and does not fall under the categories of igneous, sedimentary, or metamorphic rocks.

Breccia is a sedimentary rock composed of large, angular grains that are poorly sorted and have a detrital (siliciclastic) composition. It is not an intrusive igneous rock, does not form through metamorphism of limestone, and is not characterized by fine-grained, well-sorted particles.

Micrite / Micritic Limestone is a type of limestone that reacts with hydrochloric acid (HCL), lacks visible grains, may break with a conchoidal fracture, may contain a few visible fossils, and is composed of biochemical (bioclastic) sediment grains.

Conglomerate is a sedimentary rock that typically consists of large, rounded, gravel-sized grains. It is characterized by poorly sorted grains larger than 2mm and has a detrital (siliciclastic) composition. The incorrect answers provided describe characteristics of different types of sedimentary rocks, highlighting the distinct features of Conglomerate.

Coquina is a type of sedimentary rock with unique characteristics that set it apart from other types of rocks.

Hematitic Sandstone is characterized by sand sized grains, resulting in a rough feel, and a brown/rust color due to the presence of hematite. Option 1 describes a different type of sandstone with fine grained texture and a red color due to quartz. Option 2 describes a different type of sandstone with coarse grained texture and a yellow color due to feldspar. Option 3 describes a different type of sandstone with silt sized grains, resulting in a gritty feel, and a grey color due to the presence of iron oxide.

The correct answer for the question defines and names characteristics of rock salt, while the incorrect answers describe characteristics of other types of rocks such as granite, limestone, and marble.

Oolitic Limestone is characterized by its unique composition of ooids and its reaction with HCL, which distinguishes it from the other incorrect options provided.

Mudstone is defined by its composition, texture, and appearance, not by characteristics such as porosity, weight, color, or magnetism. It can also be found in different types of rock formations, not exclusive to sedimentary rocks.

Chalk is a soft, white sedimentary rock that is primarily composed of calcite which reacts with hydrochloric acid (HCL). Its distinct white color comes from the microscopic shells of calcareous phytoplankton or microfossils. Chalk has a biochemical or bioclastic composition due to its organic origins.

Lignite is characterized by its dull, dark brown color and brittle nature, as well as having a biochemical composition made of plant fragments and/or charcoal. It is also known for its clay-sized sediment.

Arkose is a type of sandstone that is characterized by its rough texture due to sand-sized grains and the presence of feldspar grains. It is classified under detrital (siliciclastic) composition, differentiating it from rocks like limestone which have a carbonate composition.