Algal limestone

Algal limestones are biosparites, or biomicrites, resulting from the activities of algae. 

Owen, R.W., 1973. Red Sea Algal Sediments and the Hoyt Limestone of New York A Comparison of Recent and Cambrial Algal Deposition. Thesis, Rensselaer Polytechnic Institute, Troy, New York, 117 pp. 

Oolitic limestones (or ooliths) are made up of tiny spherical grains (known as ooids) of 1 mm or less in diameter, precipitated by algal action in turbulent waters and cemented in calcite. Under a hand lens, they have the appearance of fish roe. 

Iron ore is a chemical sedimentary rock that forms when iron and oxygen (and sometimes other substances) combine in solntion and deposit as a sediment. Hematite is the most common sedimentary iron ore mineral. Rock salt (halite) is also a chemical sedimentary rock that forms from the evaporation of ocean or saline lake. It is rarely fonnd at Earth s snrface, except in areas of very arid climate and is often mined for use in the chemical indnstry or for nse as a winter highway treatment. Limestone is a rock that is composed primarily of calcinm carbonate. It can form organically from the accumulation of shell, coral, algal, and fecal debris. It can also form chemically from the precipitation of calcinm carbonate from lake or ocean water. 

Carbonate sedimentary rocks are dominantly of marine origin. Many limestones are composed of fossilised shell debris in various states of comminution, some fine grained carbonates such as chalk (q.v.) may be entirely composed of sub-microscopic phytoplankton. Algal mats secrete aragonite particles and coral reefs are CeiCO structures which may be preserved, fossilised, intact or degraded to produce other limestones. As discussed above, allochems such as faecal pellets and ooliths may be... 

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