| 词汇 | feldspar |
| 释义 | feldspar noun[ C or U ] geology specializeduk /ˈfeld.spɑːr/ us /ˈfeld.spɑːr/ a common type of mineral found especially in igneous rocks such as granite长石（一种常见矿石，尤见于火成岩，例如花岗岩中） Geology: types of rock agglomerate arenaceous arenite asthenosphere asthenospheric emery flinty gneiss haematite indurated intrusive lahar limestone lodestone magma marl marmoreal obsidian sandstone schist It contains a large proportion of mica, a small proportion of quartz and still less feldspar, but generally an abundance of iron pyrites in very minute crystals, which, on exposure, are decomposed. It is the metallic base of mica, feldspar, slate, and clay. It was made of black, glassy lava mixed with bits of feldspar. The purest clay found in nature is porcelain clay, or kaolin, which results from the decomposition of a rock composed of feldspar and quartz, and it is almost always mixed with quartz. What little feldspar there was is reduced to quartz and mica, and the quartz pebbles are drawn out into lenses. Examples of feldsparfeldspar This is conspicuous for biotite and amphibole crystals but less so in the strongly altered feldspar crystals. In these first five zones, some crystals, mainly feldspars, are visible in hand specimen. The presence of quartz-filled microcracks in feldspar crystals suggests that deformation continued during cooling and crystallization. Such spidergrams strongly suggest that these metafelsites solidified from highly fractionated melts, which underwent extensive, low pressure, accessory phases- and feldspar-dominated crystal fractionation. It is a medium-grained, foliated orthogneiss with small feldspar 'augen'. Some feldspar grains, however, show weakly developed asymmetric strain shadows (-type). The magnetic fraction of the surface sand contains pyroxene and feldspar grains as in the bulk material, but little quartz. The two planes intersect along cd which is the locus of liquids in equilibrium with a silica polymorph + two feldspars + aqueous fluid. The matrix is composed of finegrained recrystallized feldspar. Feldspar porphyroclasts have been rotated during shearing and folding. These examples are from corpora and from sources on the web. Any opinions in the examples do not represent the opinion of the Cambridge Dictionary editors or of Cambridge University Press or its licensors. |
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