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The quartz percentage among felsic minerals in TTG rocks is usually larger than 20% but less than 60%. [1] In tonalite and trondhjemite, more than 90% of the feldspars are plagioclase, while in granodiorite, this number is between 65% and 90%. [1] Trondhjemite is a special kind of tonalite, with most of the plagioclase in the rock being ...
Trondhjemite is an orthoclase-deficient variety of sodium-rich tonalite with minor biotite as the only mafic mineral, named after Norway's third largest city, Trondheim. [7] Tonalites, together with granodiorites, are characteristic of calc-alkaline batholiths formed above subduction zones. [8]
Trondhjemite is a leucocratic (light-colored) intrusive igneous rock. It is a variety of tonalite in which the plagioclase is mostly in the form of oligoclase . [ 1 ] Trondhjemites that occur in the oceanic crust or in ophiolites are usually called plagiogranites .
This list of mines in California is subsidiary to the list of mines article and lists working, defunct and future mines in the U.S. state of California. It is organized by the primary mineral output. For practical purposes stone, marble and other quarries may be included in this list.
The California State Mining and Mineral Museum exhibits and interprets the state's mineral resources and mining heritage. It is part of the California state park system, and is located near Mariposa , a town in central California, on the premises of the Mariposa County fairgrounds .
Type locality, also called type area, is the locality where a particular rock type, stratigraphic unit or mineral species is first identified. [1] If the stratigraphic unit in a locality is layered, it is called a stratotype, whereas the standard of reference for unlayered rocks is the type locality. [2] The concept is similar to type site in ...
Diorite is an intrusive igneous rock composed principally of the silicate minerals plagioclase feldspar (typically andesine), biotite, hornblende, and sometimes pyroxene.The chemical composition of diorite is intermediate, between that of mafic gabbro and felsic granite.
Because the gold in the California gravel beds was so richly concentrated, the early forty-niners simply panned for gold in California's rivers and streams, a form of placer mining. [ 10 ] [ 11 ] However, panning cannot take place on a large scale, and industrious miners and groups of miners graduated to placer mining " cradles " and "rockers ...