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Consist of particles (sediment) broken off of preexisting rocks (conglomerate, breccia, sandstone, siltstone, shale)


Consist of previously dissolved substances that precipitated from water (limestone, marl, coquina, chalk, gypsum, rock salt, dolostone, chert)


Composed of rounded particles 2 mm or larger in diameter; commonly cemented by hematite, silica, or calcite; may be of any particle composition


Same as conglomerate, but angular particles


composed of rounded or angular sand particles


composed of silt particles, gritty texture


compacted clay and silt; fissle (splits into thin sheets); most common detrital sedimentary rock


Inorganic or organic (usually organic); the consolidated equivalent of limey mud, calcareous sand, and or shell fragments; abundant calcium carbonate; freely effervescent in hydrochloric acid; the most abundant chemical precipitate


Inorganic or organic; calcareous mudstone; often beige in color


Organic form of limestone; visible shell fragments


Organic form of limestone; microscopic shells (coccoliths); used on blackboards; often white in color; often scratched by fingernail


Inorganic; hydrous calcium sulfate in rock form; scratched by fingernail

Rock salt

Inorganic; sodium chloride (halite) in rock form; tastes salty


Inorganic or organic; contains 50% or more of the mineral dolomite; reacts with HCl only if powdered


Inorganic or organic; cryptocrystalline silica (quartz); conchoidal fracture; scratches glass

Sedimentary Rocks

5% of the volume of outher 10 mi of crust. 75% on the continents.

How sedimentary rocks formed can be determined by

texture & mineral composition



Inorganic Chemical

Consist of minerals that precipitate directly from water without the action of living organisms. Evaporation is often a cause.

Organic Chemical

include remains of plants or animals, such as skeleton or shell fragments


converts sediment into rock. Compaction caused by pressure generated from weight of overlying sediment. Cementation is binding of sediment by mineral agents. Common cementing agents hematite, limonite, calcite and silica

Texture refers to

size, shape and sorting of particles that make up the rock


Large particles suggest high energy levels in the environment of deposition. For example, powerful water currents in a mountain stream could carry cobbles and boulders, but these would probably not be found in the middle of a lake, with weaker currents.


Rounding of individual particles. well-rounded particles = long transport history. Angular with sharp edges = short transport history.


well-sorted detrital rock contains particles about the same size, poorly sorted = lots of different sizes. Wind is best sorting agent, transporting mainly silt particles. Ice is poorest, carries all particle sizes

Stable minerals

last a long time at earth's surface. Quartz and hematite

Unstable minerals

Tend to weather away faster.

Red vs. black

Red contain iron oxide, which forms in oxygen-rich environments. Black have lots of organic matter, oxygen deficient environments


curve in a river


sediment accumulation at mouth of river

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