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- Feldspar - Encyclopedia. com
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
- feldspars - Encyclopedia. com
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) The potassium, sodium, and calcium end-members can be taken to represent the three apices of an equilateral triangle into which all the alkali feldspars and
- Plagioclases | Encyclopedia. com
plagioclase feldspar One of the most important rock-forming silicate minerals with the general formula (Na,Ca) (Al) 1–2 (Si) 2–3 O 8 There is a solid solution series (see PLAGIOCLASE SERIES) between the two end-members albite (Ab) (NaAlSi 3 O 8) and anorthite (An) (CaAl 2 Si 2 O 8), and the percentage of calcium end-member present is used to subdivide the series into a number of
- albitization | Encyclopedia. com
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 Source for information on albitization: A Dictionary of Earth Sciences dictionary
- alkali feldspar - Encyclopedia. com
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 CaAl 2 Si 2 O 8 (calcium
- augen-gneiss | Encyclopedia. com
augen-gneiss A medium- to coarse-grained, banded, regional metamorphic rock composed mainly of quartz and feldspar with hornblende and mica also present in variable quantities, and characterized by large ovoidal megacrysts of feldspar known as ‘augens’ (derived from the German for ‘eyes’)
- Granite | Encyclopedia. com
Granite 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 Slow cooling gives atoms time to migrate to the surfaces of growing crystals
- Bowens Reaction Series - Encyclopedia. com
The continuous arm of Bowen's reaction series represents the formation of feldspar (plagioclase ) in a continuous and gradual series that starts with calcium rich feldspar (Cafeldspar, CaAlSiO) and continues with a gradual increase in the formation of sodium containing feldspar (Ca-Na-feldspar, CaNaAlSiO) until an equilibrium is established at
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