Orthoclase is named based on the Greek for "straight fracture," because its two cleavages are at right angles to each other. Orthoclase crystallizes in the monoclinic crystal system. It has a hardness of 6, a specific gravity of 2.56-2.
Comments:
Orthoclase is the potassic variety of feldspar.
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Appearance
Orthoclase is an alkali feldspar occurring in a variety of colors, the most common being colorless.
Enhancements
Orthoclase is not enhanced.
Orthoclase :Orthoclase feldspar is a potassium aluminium silicate. It includes the attractive but infrequently seen moonstone.
Sunstone :The premier U.S. gem-quality feldspar is the red labradorite, known as sunstone, mined in Oregon.
Orthoclase: A variety of feldspar, composed of potassium aluminum silicate, characterized by a monoclinic crystalline structure and found in igneous or granitic rock. Also called potash feldspar.
Ouvarovite: See uvarovite.
Orthoclase
Orthoclase (aka feldspar) in an igneous rock forming tectosilicate (silicate) mineral and is a key component in granite.
orthoclase
Orthoclase (Potasium Aluminum Silicate or alkali feldspar or K-spar, KAlSi3O8) is named for its angles of cleavage. In Greek, orthos means "right" and kalo means "to cleave"; its two cleavages are at right angles to each other.
Orthoclase
Centerville
Topaz on Quartz - 6.8cm x 5.5cm
Aquamarine on Hematite - Former collection of Leo Horensky, 4.0cm x 3.7cm
Orthoclase - 9.7cm x 6.3cm ...
Orthoclase - usually light colored white, pink, yellow, or cream, and not transparent. The gem variety is clear to pale yellow, and some called "noble orthoclase" ...
orthoclase (embracing moonstone and adularia) and microcline (embracing amazonstone)
plagioclase (embracing sunstone, aventurine, feldspar, labradorite, and peristerite)
celsian; each with several intermediate series ...
ORTHOCLASE
Goat Fell area, Isle of Arran.
Multiple twinned crystal to 1cm.
ISLE of MULL ...
Orthoclase is common as part of the Canada Hill granite and as part of the dark hornblende gneiss visible at the mouths of the tunnels.
Moonstone (orthoclase) is a semi-translucent stone that is made of albite and orthoclase feldspar. It is usually whitish-blue, but can be colorless, yellow, orange, gray, or even reddish. Moonstone is usually set as a cabochon.
1. Talc 6. Orthoclase 2. Gypsum 7. Quartz 3. Calcite 8. Topaz 4. Fluorite 9. Corundum 5. Apatite 10 Diamond This scale is approximately linear up to corundum, but diamond is approximately 5 times harder than corundum.
Occurrence: altered orthoclase feldspar rich rocks, massive alunite
Crystal or stone size: massive crystals are rare
Comments: sometimes florescent orange in LW UV; closely resembles limestone and dolomite; a mountain of alunite is in Marysvale Utah ...
carlsbad twin Form of penetration twinning where two Orthoclase crystals form interpenetrating twins as depicted in the figure below. carving Ornamental figure, such as a stone lion, carved out of a rock or mineral.
5 - Treatment: None - Color: Soft milky white with gray and blue iridescence Is the opalescent variety of orthoclase, with a blue or white sheen like the shine of the moon.
aka Aventurine Orthoclase, Heliolite, Aventurine Feldspar
This bright, sparkling stone is a feldspar crystal formed in molten lava and then discharged onto the surface of the earth by a volcano.
Moonstone is the best known gem variety of orthoclase feldspar, being potassium aluminium silicate. It is usually polished as a cabochon, and is often carved with a moon face.
Moonstones are orthoclase feldspar with a sheen called adularescence. The most elite of the moonstones have blue flash or a rainbow of colors. The body color of these moonstones are colorless and semi-transparent.
The entire feldspar group is divided into two main branches, the potassium feldspars: microcline and orthoclase, and the sodium/calcium feldspars known as the plagioclase "series".
Moonstone is a potassium-rich orthoclase member of the feldspar group of minerals and is closely related to sunstone and labradorite. The name feldspar comes from the German feldt spat, meaning “field stone.
5a, b, and c are common forms for the mineral orthoclase and 7.5d is a common form for selenite (gypsum).
Moonstone is the most valuable form of feldspar and is composed of albite, which gives it the bluish scheen, and orthoclase feldspar.
The gem consists of pink colored orthoclase feldspar, quartz and green epidote. Best quality Unakites are nowadays used in jewelries and also in lapidary works like carvings, eggs and spheres. This stone is also known as "epidotized granite".
Granite: A common igneous rock composed of quartz, orthoclase, and hornblende, often accompanied by pyroxene or mica. It is called granite because of the granular surface. Granite is frequently used for buildings and monuments.
The particular feldspar that furnishes most of the moonstone is orthoclase, a silicate of potassium and aluminum. Another feldspar sometimes seen as a semiprecious stone is Labradorite. Amazonite, also is a feldspar.
From hardest to softest, his list includes the following: 10 is diamond, 9 is sapphire, 8 is topaz, 7 is quartz, 6 is orthoclase feldspar, 5 is apatite, 4 is fluorspar (fluorite), 3 is calcite, 2 is gypsum, and 1 is talc.
Moonstone: A variety of orthoclase feldspar that is transparent to translucent. Cut en cabochon its displays a floating blue sheen. A favourite choice of Art Nouveau jewellers.
Orthoclase Feldspar
5. Apatite
4. Fluorspar
3. Calcite
2. Gypsum
1. Talc (softest)
Because the numbers are based on properties of actual stones, they are not equally distributed.
Trachyte: A light gray igneous rock with a rough surface consisting of orthoclase feldspar.
Translucent: Allowing light to pass through, but not Transparent.
A milky sheen or wavy glowing light effect which appears to come from below the surface of the gems is known as adularescence. Orthoclase feldspar named moonstones is the only example which exhibits the true adularescence.
These include quartz (SiO2), the minerals of the feldspar group (orthoclase, K(AlSi3O8), albite Na(AlSi3O8), and anorthite (Ca(Al2Si2O8)) and muscovite mica (KAl2(AlSi3O10)(OH)2).
Double-terminated aquamarine crystal with feldspar orthoclase, 8.6 x 2.4 x 2.2 cm.
The ten-point scale of mineral hardness, keyed arbitrarily to the minerals talc, gypsum, calcite, fluorite, apatite, orthoclase, quartz, topaz, corundum, and diamond.
Treated Diamond ...
Granite is a type of igneous rock (volcanic rock that has cooled) that is light-colored and coarse grained; it is composed of at least 65% silica. Granite is characterized by the minerals orthoclase and quartz with some plagioclase feldspar and ...
This is simply a scale from 1 to 10, where 1 is the softest and 10 is hardest. (eg, quartz with a hardness of 7 will scratch orthoclase, which has a hardness of 6, diamond (hardness 10) will scratch everything).
MOHS SCALE - A loose scale of hardness, used for field collecting, which allows for identification of specimens. The comparative scale of hardness is as follows: 1) talc, 2) gypsum, 3) calcite, 4) fluorite, 5) apatite, 6) orthoclase, 7) quartz, 8) ...
Recently high quality crystals were obtained from Pike's Peak, Colorado. It was found associated with the quartz, orthoclase, and albite. Few other locations in the US yield amazonite. It is also found in pegmatite in Madagascar.
The schiller is caused by a feature of the stone's crystal structure. Orthoclase feldspar and albite are present in close association, arranged in layers. This causes an interference effect of light.
by Friedrich Mohs, a German mineralogist, as an assessment of “scratch hardness' by ranking 10 different stones from hardest to softest. His list includes the following:
10. Diamond (Hardest)
9. Sapphire
8. Topaz
7. Quartz
6. Orthoclase ...
methods, but also from the fact that various directions on a given stone's surface show a considerable variation in resistance to abrasion. The hardest direction in diamond is parallel to the faces of the octahedron.
1.Talc 6. Orthoclase feldspar
2.
Monoclinic System - A crystallization system having three unequal axes, two at an oblique angle and
a third at right angles to those two. (Gypsum, Orthoclase, etc.) ...
 See also: Mineral, Crystal, Stone, Feldspar, Color
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