American Heritage® Dictionary of the English Language, Fourth Edition
- n. Any of a group of abundant rock-forming minerals occurring principally in igneous, plutonic, and some metamorphic rocks, and consisting of silicates of aluminum with potassium, sodium, calcium, and, rarely, barium. About 60 percent of the earth's outer crust is composed of feldspar.
Century Dictionary and Cyclopedia
- n. In mineralogy, one of a very common group of closely related minerals, all silicates of aluminium, together with either calcium, sodium, potassium, or in one case barium. They crystallize in the monoclinic or triclinic system with closely similar angles. The prismatic angle is not far from 120°, and they have two easy cleavages which make an angle of 90°, or nearly 90°, with each other. Their specific gravity lies between 2.6 and 2.8, and their hardness between 6 and 7. In color they vary from clear and glassy to white, grayish, and light shades of yellow, red, or green, rarely darker green to black. They occur in distinct crystals, also in massive forms varying in structure from coarsely cleavable to granular-crystalline, compact, and hornstone-like. They form an essential constituent of many of the common crystalline rocks, as granite, gneiss, syenite, diorite, most kinds of basalt, andesite, trachyte, etc. The monoclinic feldspars are orthoclase and hyalophane. The former is a potash feldspar (see
orthoclase), and is the commonest of the group; the latter is a baryta feldspar, and is a rare species. Closely related to orthoclase is the triclinic microcline (which see), having the same composition, but varying slightly in form. Besides these there are the triclinic (lime-soda) feldspars, called in general plagioclase, because of the oblique angle between their two cleavages, and forming a series varying progressively in composition, form, optical characters, and specific gravity from the lime feldspar anorthite to the sodium feldspar albite; the intermediate species are considered as isomorphous compounds of these two extremes in varying proportions. Those ordinarily recognized are, named in order, labradorite, andesin, and oligoclase, the last approaching most closely to albite. The increase in soda in the members of the series is accompanied by an increase of silica, the species being increasingly acidic in the order named: thus, anorthite contains 43 per cent, of silica, and albite 69 per cent. The specific gravity diminishes in the series from anorthite (2.75) to albite (2.61). Certain triclinic feldspars containing considerable potash and with an angle of cleavage varying but little from 90° are sometimes grouped under the name anorthoclase. Common feldspar, or orthoclase (and microcline), is much used in the manufacture of porcelain; some kinds are employed for ornaments, as aventurin feldspar or sunstone, also moonstone (an opalescent variety of orthoclase), albite or oligoclase, and, most of all, the species labradorite, beautiful for its play of colors Also felspar.
- n. mineralogy Any of a large group of rock-forming minerals that, together, make up about 60% of the earth's outer crust. The feldspars are all aluminum silicates of the alkali metals sodium, potassium, calcium and barium. Feldspars are the principal constituents of igneous and plutonic rocks.
GNU Webster's 1913
- n. (Min.) A name given to a group of minerals, closely related in crystalline form, and all silicates of alumina with either potash, soda, lime, or, in one case, baryta. They occur in crystals and crystalline masses, vitreous in luster, and breaking rather easily in two directions at right angles to each other, or nearly so. The colors are usually white or nearly white, flesh-red, bluish, or greenish.
- n. any of a group of hard crystalline minerals that consist of aluminum silicates of potassium or sodium or calcium or barium
- Feld, field (from Middle High German veld, from Old High German feld) + Spath, spar (Wiktionary)
- Partial translation of obsolete German Feldspath : Feld, field (from Middle High German veld, from Old High German feld; see pelə-2 in Indo-European roots) + Spath, spar. (American Heritage® Dictionary of the English Language, Fourth Edition)
“The name feldspar is a contraction of the longer name fieldspar, as some early specimens were found in fields.”
“Sand, the proppant, primarily quartz and feldspar aka ground up rock, is the material that gets lodged in cracks that open up, and keep those cracks open when force and pressure are removed, allowing less resistance between underground hydrocarbons, to allow them to become newly liberated hydrocarbons, which we use to power a significant portion of our country.”
“(Common orthoclase feldspar, which is frequently of a brownish pink or flesh color, will do.)”
“In other cases, quartz is the predominant material, and in still other cases, where the best kaolin is produced, the proportion of both quartz and mica are small, and the feldspar is the prevailing material.”
“Simple inspection will show that granite rock, for example, is a mixture of three minerals, called feldspar, mica, and quartz.”
“The rock here is a porphyritic granite (porhyritic meaning that the stone has large-grained crystals, such as feldspar or quartz, dispersed in a fine-grained feldspathic matrix or groundmass).”
“In the process of weathering, the softer, weaker minerals in granite (such as feldspar) are weathered away.”
“Melters such as feldspar, whiting (or limestone) and talc are sufficient for the higher temperatures above 1200”
“There is also added some more fusible substance, such as feldspar, gypsum, or lime, together with some pure quartz.”
“Basalt includes smaller amounts of light colored minerals such as feldspar and quartz.”
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List of minerals, elements, group names and geochemistry terms encountered in the science of mineralogy. I've chosen to avoid capital letters in most examples, though a great many mineral names hon...
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From the story by Jules Verne.
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