Norite

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norite

[′nȯ‚rīt]
(petrology)
A coarse-grained plutonic rock composed principally of basic plagioclase with orthopyroxene (hypersthene) as the dominant mafic material. Also known as hypersthenfels.

Norite

 

(Norwegian norit, from Norge, “Norway”), a rock of basic composition in the gabbro group. It differs from gabbro in that it contains a rhombic pyroxene, usually bronzite but sometimes enstatite and hypersthene. When both pyroxenes are present the rock is called gabbro-norite. The remaining minerals are those in gabbro. Plagioclase with more than 50 percent anorthite predominates; olivine is often present; and various ore minerals such as magnetite, titanmagnetite, and sulfides occur as insignificant impurities. Norite typically has a low SiO2 content (45–55 percent), significant amounts of Mg and Ca (10–20 percent), and a negligible alkali content (rarely more than 2–3 percent). It is used as a building material.