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Plagioclase; dark minerals. Alkali feldspar granite, some varieties of which are called 'red granite', [1] is a felsic igneous rock and a type of granite rich in the mineral potassium feldspar (K-spar). It is a dense rock with a phaneritic texture. The abundance of K-spar gives the rock a predominant pink to reddish hue; peppered with minor ...
Granite. Granite (/ ˈɡrænɪt / GRAN-it) is a coarse-grained (phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies underground.
Feldspar. Feldspar (/ ˈfɛl (d) ˌspɑːr / FEL (D)-spar; sometimes spelled felspar) is a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. [3] The most common members of the feldspar group are the plagioclase (sodium-calcium) feldspars and the alkali (potassium ...
Larvikite. Polished larvikite (marketed as "Blue Pearl Granite"), showing labradorescence, is a popular decorative stone. Larvikite is an igneous rock, specifically a variety of monzonite, [1] notable for the presence of thumbnail-sized crystals of feldspar. These feldspars are known as ternary because they contain significant components of all ...
Quoting Tuttle and Bowen in 1958 (abstract, page 3): ″ A classification of salic rocks based on the nature of the alkali feldspar is proposed. The classification has two major divisions: (1) subsolidus, and (2) hypersolvus, depending on the whereabouts of the soda feldspar. In the hypersolvus rocks all the soda feldspar is or was in solid ...
Like all granites, the modal mineralogy of S-type granites are dominated by alkali - and plagioclase feldspars and quartz. Thus, S-type granites are silica over-saturated (contain quartz), and do not contain feldspathoids. An interesting feature of S-type granites, at the hand sample scale, is that alkali-feldspars are typically white in color ...
Aplite, showing fine-grained texture. Aplite (/ ˈæplaɪt /) is an intrusive igneous rock that has a granitic composition. Aplites are fine-grained to aphanitic (without grains visible to the naked eye) and may consist of only quartz and feldspar or the term may refer to any leucocratic (pale-coloured) minor intrusion of that grain size. [1]
Rapakivi granite. Rapakivi granite is an igneous intrusive rock and variant of alkali feldspar granite. It is characterized by large, rounded crystals of orthoclase each with a rim of oligoclase (a variety of plagioclase). Common mineral components include hornblende and biotite. The name has come to be used most frequently as a textural term ...