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An ore deposit is any geological, or nonrenewable, material that can be mined at a profit. The feldspars are the most abundant and widespread minerals of the crust, or outermost part, of the Earth. Because of their abundance, feldspars are used in the classification of IGNEOUS ROCKSFeldspars are used in the manufacture of ceramics and ceramic glazes and as mild abrasives. A few varieties, including labradorite and orthoclase, are occasionally used as gems because they …

…BASALT rocks contain plagioclase, magnesium, and iron-rich minerals, such as olivine or pyroxene. The sea floors and many oceanic islands, including Iceland and Hawaii, are composed of basalt. Basalt also makes up the lunar mare, or lowlands. ANDESITE, the volcanic rock of the Andes, the Cascades, and many other mountain ranges, contains substantial plagioclase. Plagioclase weathers more readily than alkali feldspars and is less common in sediments and sedimentary rocks. ------------------------------------------------------------------------ **Bibliography** www.igneousrock.com