orthoclase feldspar
71Aplite — (pronEng|ˈæplaɪt) in petrology, the name given to intrusive rock in which quartz and feldspar are the dominant minerals. Aplites are usually very fine grained, white, grey or pinkish, and their constituents are visible only with the help of a… …
72Quartz-porphyry — Quartz porphyry, in petrology, is the name given to a group of hemi crystalline acid rocks containing porphyritic crystals of quartz in a fine grained matrix, usually of micro crystalline or felsitic structure. In specimens, the quartz appears as …
73Syenogranite — is a fine to coarse grained intrusive igneous rock of the same general composition as granite. They are characteristically felsic. The feldspar component of syenogranite is predominantly alkaline in character (usually orthoclase). For example,… …
74Barringer Hill — is a famous geological and mineralogical site in central Texas. It lies on the former west side of the Colorado river, beneath Lake Buchanan, about convert|22|mi|km northeast of the town of Llano. The hill consists of a pegmatite and geologically …
75Subsolvus — In subsolvus granites, which crystallisation occurs at great water pressures, two types of feldspar are present as opposed to hypersolvus granites in which crystallization at relatively low water pressures results in the formation of a single… …
76perthite — perthitic /peuhr thit ik/, adj. perthitically, adv. /perr thuyt/, n. Mineral a variety of feldspar containing irregular bands of albite in microcline. [1832; named after Perth, Ontario, Canada; see ITE1] * * * any member of a class of… …
77mohs' scale — ˈmōz , ōs(ə̇z) noun Usage: usually capitalized M Etymology: after Friedrich Mohs died 1839 German mineralogist 1. : a scale of hardness for minerals ranging from 1 for the softest to 10 for the hardest in which 1 represents the hardness of talc;… …
78Amazonite — (sometimes called Amazon stone ) is a green variety of microcline feldspar.The name is taken from that of the Amazon River, from which certain green stones were formerly obtained, but it is doubtful whether green feldspar occurs in the Amazon… …
79Mineral — For other uses, see Mineral (disambiguation). An assortment of minerals. A mineral is a naturally occurring …
80Rubidium-strontium dating — The rubidium strontium dating method is a radiometric dating technique that geologists use to determine the age of rocks.Development of this process was aided by Fritz Strassmann, who later moved onto discovering nuclear fission with Otto Hahn… …
