Augite
21Leucite — is a rock forming mineral composed of potassium and aluminium tectosilicate K [AlSi2O6] . Crystals have the form of cubic icositetrahedra but, as first observed by Sir David Brewster in 1821, they are not optically isotropic, and are therefore… …
22Trachyte — is an igneous, volcanic rock with an aphanitic to porphyritic texture. The mineral assemblage consists of essential alkali feldspar; relatively minor plagioclase and quartz or a feldspathoid such as nepheline may also be present. (See the QAPF… …
23Augit — Kristallstufe aus der La Pancita Mine, Oaxaca, Mexiko Chemische Formel (Ca,Fe)(Mg,Fe)[Si2O6] Mineralklasse …
24picrite — /pik ruyt/, n. a granular igneous rock composed chiefly of olivine and augite, but containing small amounts of feldspar. [1805 15; < Gk pikr(ós) bitter + ITE1] * * * ▪ rock intrusive igneous rock of ultramafic (very silica poor) composition …
25Geochemistry — The field of geochemistry involves study of the chemical composition of the Earth and other planets, chemical processes and reactions that govern the composition of rocks and soils, and the cycles of matter and energy that transport the Earth s… …
26Nepheline syenite — of the Intrusive Complex of Tanguá, State of Rio de Janeiro, Brasil (Motoki et al., 2011a) Nephelene syenite is a holocrystalline plutonic rock that consists largely of nepheline and alkali feldspar. The rocks are mostly pale colored, grey or… …
27Tachylite — (also spelled tachylyte) is a vitreous form of basaltic volcanic glass. This glass is formed naturally by the rapid cooling of molten basalt. It is a basic type of igneous rock that is decomposable by acids and readily fusible. The color is a… …
28basalt — basaltic, basaltine /beuh sawl tin, tuyn/, adj. /beuh sawlt , bas awlt, bay sawlt/, n. the dark, dense igneous rock of a lava flow or minor intrusion, composed essentially of labradorite and pyroxene and often displaying a columnar structure.… …
29DOLÉRITES — Roches magmatiques intermédiaires entre les gabbros (roches plutoniques grenues) et les basaltes (roches volcaniques microlitiques). Massives, grises ou noires, de structure microgrenue, les dolérites sont constituées par des plagioclases… …
30Basalt — For the World War II raid, see Operation Basalt. For the cities, see Basalt, Colorado and Basalt, Idaho. Basalt Igneous Rock Composition …
