sedimentary rock types 2

• Organic sedimentary rocks are composed of the remains of once-living organisms, including animals and plants.
• Chalk is a type of limestone made of microscopic marine plankton shells called coccoliths.
• Shelly limestone/bio-clastic limestone contains fossils held together by a calcium carbonate cement and reacts with dilute hydrochloric acid.
• Reef limestone/coral limestone is made from preserved coral fossils found in shallow tropical water deposits.
• Coal is a carbon-rich mineral deposit formed from the remains of dead plant matter in tropical climates in anaerobic swamps.
• Peat has the lowest carbon content density and hardness, followed by lignite, bituminous coal, and anthracite.
• Peat is semi-decomposed plant material with recognizable vegetation structure, containing 50% carbon and burning poorly with lots of smoke.
• Lignite/brown coal contains 60-70% carbon and often looks woody, generating smoke and ash when burned.
• Bituminous coal is black in color, breaks into fragments, and can have bands of dull and shiny layers, containing 80-85% carbon.
• Anthracite contains 90-95% carbon, burns slowly with no smoke, and has a vitreous and metallic appearance.
• Chemical sedimentary rocks are formed by the precipitation of material from solution.
• Oolitic limestone is made of spherical ooliths set in a calcite cement, forming in shallow, high-energy tropical waters.
• Evaporites are materials precipitated from seawater, with the order of precipitation from least soluble to most soluble being calcite, gypsum/anhydrite, halite, and potassium/magnesium salts.
• Water in lagoons evaporates and precipitates a thin layer of evaporites, with multiple cycles of evaporation and replenishment creating thick beds.