Oligoclase is a rock-forming mineral belonging to the plagioclase feldspars. In chemical composition and in its crystallographic and physical characters it is intermediate between albite (NaAlSi₃O₈) and anorthite (CaAl₂Si₂O₈). The albite : anorthite molar ratio ranges from 90 : 10 to 70 : 30. This article is about minerals in the geologic sense; for nutrient minerals see dietary mineral; for the band see Mineral (band). ... Lunar Ferroan Anorthosite #60025 (Plagioclase Feldspar). ... Feldspar is the name of an important group of rock-forming minerals which make up perhaps as much as 60% of the Earths crust. ... Albite, a feldspar mineral, is a member of the plagioclase series. ... Anorthite is one of the plagioclase feldspars, an important group of minerals abundant in the Earths crust. ...

Oligoclase is a high sodium feldspar crystallizing in the triclinic system. The Mohs hardness is 6 to 6.5 and the specific gravity is 2.64 to 2.66. The refractive indices are: nα=1.533 - 1.543, nβ=1.537 - 1.548, and nγ=1.542 - 1.552. In color it is usually white, with shades of grey, green or red. In crystallography, the triclinic crystal system is one of the 7 lattice point groups. ... Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer. ... Relative density (also known as specific gravity) is a measure of the density of a material. ... The refractive index of a material is the factor by which the phase velocity of electromagnetic radiation is slowed relative to vacuum. ...

The name oligoclase was given by August Breithaupt in 1826 from the Greek oligos, little, and kasein, to break, because the mineral was thought to have a less perfect cleavage than albite. It had previously been recognized as a distinct species by J. J. Berzelius in 1824, and was named by him soda-spodumene (Natron-spodumen), because of its resemblance in appearance to spodumene. Jöns Jacob Berzelius (August 20, 1779 - August 7, 1848) was a Swedish chemist, who invented modern chemical notation and is considered one of the fathers of modern chemistry (along with John Dalton and Antoine Lavoisier). ... Spodumene is a pyroxene mineral consisting of lithium aluminium inosilicate - LiAl(SiO3)2 - and is a source of lithium. ...

Perfectly colorless and transparent glassy material found at Bakersville, North Carolina has occasionally been faceted as a gemstone. Another variety more frequently used as a gemstone is the aventurine-feldspar or sun-stone found as reddish cleavage masses in gneiss at Tvedestrand in southern Norway; this presents a brilliant red to golden metallic glitter, due to the presence of numerous small scales of hematite oriented within the feldspar structure. Bakersville is a town located in Mitchell County, North Carolina. ... A selection of gemstone pebbles made by tumbling rough rock with abrasive grit, in a rotating drum. ... Aventurine is a form of quartz, characterised by its translucency and the presence of platy mineral occlusions that give a shimmering or glistening effect termed aventurescence. ... Banded gneiss with dike of granite orthogneiss Gneiss is a common and widely distributed type of rock formed by high grade regional metamorphic processes from preexisting formations that were originally either igneous or sedimentary rocks. ... County Aust-Agder Landscape Sørlandet Municipality NO-0938 Administrative centre Tvedestrand Mayor (2004) Jan Dukene (Tvedestrand Tverrpolitiske Liste) Official language form Bokmål Area  - Total  - Land  - Percentage Ranked 322 218 km² 204 km² 0. ... Hematite (AE) or haematite (BE) is the mineral form of Iron (III) oxide, (Fe2O3), one of several iron oxides. ...

Oligoclase occurs, often accompanying orthoclase, as a constituent of plutonic igneous rocks such as granite, syenite, and diorite. It occurs in porphyry and diabase dikes and sills as well as in the volcanic rocks andesite and trachyte. It also occurs in gneiss. The best developed and largest crystals are those found with orthoclase, quartz, epidote and calcite in veins in granite at Arendal in Norway. The distinctive texture of rapakivi granite is due to oligoclase rims on orthoclase phenocrysts. Feldspar (from the German Feld, field, and Spat, a rock that does not contain ore) is the name of an important group of rock-forming minerals which make up perhaps as much as 60% of the Earths crust. ... Volcanic rock on North America Plutonic rock on North America Igneous rocks are formed when molten rock (magma) cools and solidifies, with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks. ... Quarrying granite for the Mormon Temple, Utah Territory. ... Syenite Syenite is a coarse-grained intrusive igneous rock of the same general composition as granite but with the quartz either absent or present in relatively small amounts. ... Categories: Mineral stubs | Igneous rocks ... Porphyry (Greek Πορφύριος purple-clad) may refer to: Porphyry of Tyros (c. ... Diabase is a mafic, holocrystalline, igneous rock equivalent to volcanic basalt or plutonic gabbro. ... A dike in geology refers to a tabular intrusive igneous body. ... In geology, a sill is a tabular, often horizontal mass of igneous rock that has been intruded laterally between older layers of sedimentary rock, beds of volcanic lava or tuff, or even along the direction of foliation in metamorphic rock. ... This article is about volcanoes in geology. ... A sample of andesite (dark groundmass) with amygdaloidal vesicules filled with zeolite. ... Trachyte is an igneous, volcanic rock with an aphanitic to porphyritic texture. ... Quartz is the most abundant mineral in the Earths continental crust. ... Epidote is a calcium aluminium iron sorosilicate mineral, Ca2(Al, Fe)3(SiO4)3(OH), crystallizing in the monoclinic system. ... Doubly refracting Calcite from Iceberg claim, Dixon, New Mexico. ... Arendal (N 58 27, E 8 56) is a town in the county of Aust-Agder, Norway. ... Rapakivi granite is a hornblende-biotite granite containing large rounded crystals of orthoclase mantled with oligoclase. ... Example of phenocrysts in rhomb porphyry from the Oslo rift area in Norway A phenocryst is a relatively large and usually conspicuous crystal formed in the mass of a porphyritic igneous rock. ...

References

• This article incorporates text from the 1911 Encyclopædia Britannica, a publication in the public domain.
• Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., Wiley, ISBN 0471805807
• Webmineral data
• Mineral galleries
• Mindat