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Pegmatite. A pegmatite is an igneous rock showing a very coarse texture, with large interlocking crystals usually greater in size than 1 cm (0.4 in) and sometimes greater than 1 meter (3 ft). Most pegmatites are composed of quartz, feldspar, and mica, having a similar silicic composition to granite.
Petalite. Petalite, also known as castorite, is a lithium aluminum tektosilicate mineral Li Al Si 4 O 10, crystallizing in the monoclinic system. Petalite occurs as colorless, pink, grey, yellow, yellow grey, to white tabular crystals and columnar masses. It occurs in lithium-bearing pegmatites with spodumene, lepidolite, and tourmaline.
Lepidolite is associated with other lithium-bearing minerals like spodumene in pegmatite bodies. It is the major source of the alkali metal rubidium. [13] In 1861, Robert Bunsen and Gustav Kirchhoff extracted 150 kg (330 lb) of lepidolite to yield a few grams of rubidium salts for analysis, and therefore discovered the new element rubidium. [14 ...
Granite (light) with sheeted veins of greisen (dark) at Cligga Head, Cornwall. Greisen is a highly altered granitic rock or pegmatite, usually composed predominantly of quartz and micas (mostly muscovite). Greisen is formed by self-generated alteration of a granite and is a class of moderate- to high-temperature magmatic-hydrothermal alteration ...
The principal sources of rare-earth elements are the minerals bastnäsite (RCO 3 F, where R is a mixture of rare-earth elements), monazite (XPO 4, where X is a mixture of rare-earth elements and sometimes thorium), and loparite ((Ce,Na,Ca)(Ti,Nb)O 3), and the lateritic ion-adsorption clays.
Miarolitic cavities (or miarolitic texture) are typically crystal-lined irregular cavities or vugs most commonly found in granitic pegmatites, and also in a variety of igneous rocks. The central portions of pegmatites are often miarolitic as the pegmatite dike crystallizes from the outside walls toward the center. The volatile portion of the ...
These aplite-pegmatite sheet complexes may show fine-scale banding with alternations of aplite and pegmatite. [ 4 ] Syenite -aplites consist mainly of alkali feldspar; the diorite-aplites of plagioclase ; there are nepheline -bearing aplites, including those containing the elaeolite variety of nepheline.
Uranium minerals were derived from uraniferous pegmatites in the sediment source areas. These deposits are restricted to the Archean and early Paleoproterozoic and do not occur in sediments younger than about 2,200 million years when oxygen levels in the atmosphere reached a critical level, making simple uranium oxides no longer stable in near ...