May 29, 2018 · Feldspar Feldspar is the most common mineral on Earth [1], constituting approximately 60% of the crust . It forms directly from cooling magma and is a major component of granite and most other igneous rocks .

May 8, 2018 · feldspars The most important group of rock-forming silicate minerals, including the alkali feldspars KAlSi 3 O 8 to NaAlSi 3 O 8 (K-feldspar to albite) and the plagioclase feldspars NaAlSi 3 O 8 to CaAl 2 Si 2 O 8 (albite to anorthite).

May 8, 2018 · alkali feldspar A group of silicate minerals that contain the alkali metal elements potassium and sodium. The normal feldspar minerals (including the calcium-bearing varieties) can be plotted on a chemical basis into a triangle which has KAlSi 3 O 8 (potassium feldspar, sanidine, orthoclase (Or), or microcline), NaAlSi 3 O 8 (sodium feldspar, albite, or Ab), and …

May 8, 2018 · Plagioclase Plagioclase is a form of the mineral feldspar . All feldspars are crystals of aluminum, oxygen , and silicon , plus a major additive. In the case of plagioclase, the additive is calcium, sodium, or a blend of both. Miscellaneous impurities may also be present.

May 8, 2018 · Granite, which makes up 70 – 80% of Earth's crust, is an igneous rock formed of interlocking crystals of quartz, feldspar, mica, and other minerals in lesser quantities. Large masses of granite are a major ingredient of mountain ranges. Granite is a plutonic rock, meaning that it forms deep underground.

albitization The partial or complete replacement of pre-existing plagioclase feldspar or alkali feldspar by albite. There are a number of ways in which this can be achieved. A common process involves the residual water-rich vapour released during the final stages of crystallization of a …

May 29, 2018 · When exposed to water, some of these minerals (e.g., feldspar) decay chemically faster than others (especially quartz), allowing the granite to crumble into fragments. Sand formed by weathering is termed epiclastic. Where fragmentation is rapid, granite crumbles before its feldspar has fully decayed and the resulting sand contains more feldspar.

Solid solution series A solid solution series is the compositional range between end-member minerals that share the same basic chemical formula but experience substitution of elements in one or more atomic sites.

kaolinitization (kaolinization) Hightemperature hydrothermal alteration (see HYDROTHERMAL ACTIVITY) and replacement of feldspars, to varying degrees, to form a fine-grained aggregate of the mineral

May 17, 2018 · Miners and mineralogists had long been accustomed to scratch a mineral to aid in determining the species. In an attempt to make this method more certain, Mohs proposed a scale of increasing hardness from one to ten as follows: talc, 1; gypsum, 2; calcite, 3; fluorite, 4; apatite, 5; feldspar, 6; quartz, 7; topaz, 8; corundum, 9; and diamond, 10.