Geological Properties Of Andesine
Geological Properties Of Andesine – What Is Andesine
Andesine is a silicate mineral, a member of the plagioclase feldspar solid solution series. Its chemical formula is (Ca, Na)(Al, Si)4O8, where Ca/(Ca + Na) (% Anorthite) is between 30%-50%. The plagioclase feldspars are a continuous solid solution series and as such the accurate identification of individual members requires detailed optical study, chemical analysis or density measurements. Refractive indices and specific gravity increase directly with calcium content.
Andesine feldspar is composed of 50-70% albite and 30-50% anorthite.
Andesine Labradorite Varieties or Similar Gemstones
Andesine-labradorite belongs to the feldspar group of minerals, which is Earth’s most abundant mineral group. Feldspars make up nearly 60% of the Earth’s crust and are distinguished by the presence of aluminum and silica ions, including aluminum silicates; sodium oxide, potassium oxide and calcium oxide.
The two main feldspar branches are plagioclase feldspar (labradorite and sunstone) and potassium feldspar, which includes orthoclase and microcline. Plagioclase gemstones all have similar hardness scores and relatively high refractive indices, ranging between beryl and quartz. All are mixtures of albite and anorthite. Andesine is 50-70% albite (a sodium aluminum silicate) and 30-50% anorthite (a calcium aluminum silicate), while labradorite is 50-70% anorthite and 30-50% albite. Since these two materials vary in ratio, it is easy to see why andesine-labradorite can be so confusing. Plagioclase feldspars have a similar appearance and they can often be categorized as both andesine and labradorite.
Geological Properties Of Andesine
There are a few gemstones that appear similar to andesine-labradorite, but andesine-labradorite can be distinguished through simple observations. Andesine-labradorite is sometimes intentionally traded as ‘Oregon sunstone’, because sunstone typically has a higher price-per-carat value. ‘Rainbow moonstone’ is a variety of labradorite that goes by many trade names, such as ‘blue-rainbow moonstone’, ‘labradorite-moonstone’ and ‘blue-sheen labradorite’; but all of these refer to a gem closely related to andesine-labradorite and not actually ‘moonstone’.
Occurrence and Properties of Andesine
It is mostly found in magmatic and metamorphic environment. It typically occurs in metamorphic rocks of granulite, usually showing antiperthite property. It occurs in the form of intermediate igneous rocks such as Diorite, Andesite and Syenite. This substance is also found as detrital grains in sedimentary rocks. This chemical is closely related with Quartz, Potassium Feldspar and Magnetite.
A fairly new gemstone shrouded in mystery, andesine is believed to have been discovered in the Congo near the Nyaragongo Volcano sometime in 2003. The gemstone’s name comes from the Andes of South America. Andesine was originally traded without disclosure of color enhancements. Much of what was originally introduced to the gemstone market as andesine is not truly andesine and is actually enhanced labradorite, a fellow plagioclase feldspar. Andesine has a faint metallic schiller called labradorescence and exhibits a range of color known as pleochroism.
Name and discovery
Andesine was first described in 1841 for an occurrence in the Marmato mine, Colombia. It is named after the Andes mountains of South America. The name is for the Andes due to its abundance in the andesite lavas in those mountains.
Andesine is found in a range of colors, from red, honey-red to orange, yellow, champagne and green. In the early 2000s, red and green gemstones began to be marketed under the name of ‘Andesine’. After some controversy, these gemstones were subsequently discovered to have been artificially-colored.
Occurrence
Andesine occurs in intermediate igneous rocks such as diorite, syenite and andesite. It characteristically occurs in metamorphic rocks of granulite to amphibolite facies commonly exhibiting antiperthite texture. It also occurs as detrital grains in sedimentary rocks. It is commonly associated with quartz, potassium feldspar, biotite, hornblende and magnetite.
Andesine Labradorite Gemstone and Jewelry Care and Cleaning
Andesine-labradorite is a relatively soft stone. Since ordinary dust often contains traces of quartz (with a hardness of 7 on the Mohs scale), simply wiping off dust can result in reduced polish and surface scratches, marring andesine-labradorite’s desirable luster. Do not wear andesine-labradorite stones whilst participating in vigorous physical activities, such as sports and exercise, and always take off jewelry before engaging in household chores. Warm water and a soft cloth can be used to clean andesine-labradorite gemstones and if needed, a mild soap can be used. Be sure to rinse gemstones well to remove soapy residue. As with almost all gemstones, avoid any ultrasonic cleaners and steam cleaners. Heating can permanently alter or damage andesine-labradorite color. When storing andesine-labradorite and other gemstones, store them separately from one another. Harder gems, especially diamonds, rubies and sapphires, can easily scratch andesine-labradorite, so it is recommended to always wrap them in a soft cloth or place them in a fabric-lined box.
Uses of Andesine
Andesine is chiefly used as a gemstone. Earlier, this gemstone was supposed to be better when left untreated. Today, however, heat treatment is commonly used to process this material and bring out its true color. The gemstone is also used in engraving and in artworks like decorative boxes. This stone is also used in the ceramic industry and in tiles, stones, and bricks.
Geological Properties Of Andesine
Andesine should not be confused with Sunstone, which is a natural reddish feldspar gem. Sometimes Andesine gems are intentionally mislabeled as Oregon Sunstone to promote higher prices. Sunstone can easily be distinguished by its glitter effect or aventurescence. The red gemstones Ruby, Spinel, and Rubellite Tourmaline are all harder then Andesine.
Physical Properties of Andesine
Chemical Formula: (Na,Ca)Al1-2Si3-2O8
Color: Red, Green, Yellow, Orange, Pink, Multicoloured
Hardness: 6 – 6.5
Crystal System: Triclinic
Refractive Index: 1.560 – 1.568
SG: 2.69 – 2.70
Transparency: Transparent to translucent
Double Refraction .008
Luster: Vitreous
Cleavage: 2,1 – basal ; 2,1 – prismatic ; 3,1 – pinacoidal.
Mineral Class: Plagioclase feldspar
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