Last updated
Category microcline or oligoclase and orthoclase variety
(repeating unit)
Crystal system Triclinic
ColorColorless, orange, yellow, red, green, blue, brown and copper shiller
Crystal habit Euhedral crystals, granular
Twinning Lamellar
Cleavage 001
Mohs scale hardness6.0–6.5
Diaphaneity Transparent to translucent and opaque
Specific gravity 2.64–2.66
Refractive index 1.525–1.58

Sunstone is a microcline or oligoclase feldspar, which when viewed from certain directions exhibits a spangled appearance. It has been found in Southern Norway, Sweden, various United States localities and on some beaches along the midcoast of South Australia.



Physical properties

Unpolished sunstone Sunstone2.jpg
Unpolished sunstone

The optical effect is due to reflections from inclusions of red copper, hematite, or goethite, in the form of minute scales, which are hexagonal, rhombic, or irregular in shape, and are disposed parallel to the principal cleavage-plane. These inclusions give the stone an appearance something like that of aventurine, hence sunstone is known also as "aventurine-feldspar". The optical effect is called schiller and the color of Oregon Sunstone is due to copper. The middle part of this crystal sparkles, and usually the color is darkest in the middle and becomes lighter toward the outer edges.

The feldspar which usually displays the aventurine appearance is oligoclase, though the effect is sometimes seen in orthoclase: hence two kinds of sunstone are distinguished as "oligoclase sunstone" and "orthoclase sunstone".


Sunstone was not popular until recently.[ when? ] Previously the best-known locality being Tvedestrand, near Arendal, in south Norway, where masses of the sunstone occur embedded in a vein of quartz running through gneiss.

Other locations include near Lake Baikal in Siberia, and several United States localities—notably at Middletown Township, Delaware County, Pennsylvania; Plush, Oregon; and Statesville, North Carolina.

A small rolled sunstone A small polished sunstone.jpg
A small rolled sunstone

The "orthoclase sunstone" variant has been found near Crown Point and at several other localities in New York, as also at Glen Riddle in Delaware County, Pennsylvania, and at Amelia Courthouse, Amelia County, Virginia.

Sunstone is also found in Pleistocene basalt flows at Sunstone Knoll in Millard County, Utah. [1]

Andesine controversy

Various gem colors of Oregon sunstone Labradoriteoregonsunstone.jpg
Various gem colors of Oregon sunstone

In the early 2000s, a new variety of red or green gemstone resembling sunstone and known as "Andesine" appeared in the gem market. After much controversy and debate, most of these gemstones, allegedly sourced from China, were subsequently discovered to have been artificially colored by a copper diffusion process. [2] A Tibetan source of bona fide (untreated) red andesine, however, was eventually verified by a number of independent groups of well-respected gemologists. [3] [4] [5] [6] [7]

Oregon sunstone

A variety known as "Oregon sunstone" is found in Harney County, Oregon and in eastern Lake County north of Plush. Oregon Sunstone contains elemental copper. [8] Oregon Sunstone is unique in that crystals can be quite large. The copper leads to variant color within some stones, where turning one stone will result in manifold hues: the more copper within the stone, the darker the complexion. [9]

On August 4, 1987, the Oregon State Legislature designated Oregon Sunstone as its state gemstone by joint resolution. [10]

See also

Related Research Articles

<span class="mw-page-title-main">Amazonite</span> Green silicate mineral

Amazonite, also known as Amazonstone, is a green tectosilicate mineral, a variety of the potassium feldspar called microcline. Its chemical formula is KAlSi3O8, which is polymorphic to orthoclase.

<span class="mw-page-title-main">Amblygonite</span>

Amblygonite is a fluorophosphate mineral, (Li,Na)AlPO4(F,OH), composed of lithium, sodium, aluminium, phosphate, fluoride and hydroxide. The mineral occurs in pegmatite deposits and is easily mistaken for albite and other feldspars. Its density, cleavage and flame test for lithium are diagnostic. Amblygonite forms a series with montebrasite, the low fluorine endmember. Geologic occurrence is in granite pegmatites, high-temperature tin veins, and greisens. Amblygonite occurs with spodumene, apatite, lepidolite, tourmaline, and other lithium-bearing minerals in pegmatite veins. It contains about 10% lithium, and has been utilized as a source of lithium. The chief commercial sources have historically been the deposits of California and France.

<span class="mw-page-title-main">Beryl</span> Gemstone: beryllium aluminium silicate

Beryl ( BERR-əl) is a mineral composed of beryllium aluminium silicate with the chemical formula Be3Al2Si6O18. Well-known varieties of beryl include emerald and aquamarine. Naturally occurring, hexagonal crystals of beryl can be up to several meters in size, but terminated crystals are relatively rare. Pure beryl is colorless, but it is frequently tinted by impurities; possible colors are green, blue, yellow, pink, and red (the rarest). It is an ore source of beryllium.

<span class="mw-page-title-main">Sapphire</span> Gem variety of corundum

Sapphire is a precious gemstone, a variety of the mineral corundum, consisting of aluminium oxide (α-Al2O3) with trace amounts of elements such as iron, titanium, chromium, vanadium, or magnesium. The name sapphire is derived via the Latin "sapphirus" from the Greek "sappheiros", which referred to lapis lazuli. It is typically blue, but natural "fancy" sapphires also occur in yellow, purple, orange, and green colors; "parti sapphires" show two or more colors. Red corundum stones also occur, but are called rubies rather than sapphires. Pink-colored corundum may be classified either as ruby or sapphire depending on locale. Commonly, natural sapphires are cut and polished into gemstones and worn in jewelry. They also may be created synthetically in laboratories for industrial or decorative purposes in large crystal boules. Because of the remarkable hardness of sapphires – 9 on the Mohs scale (the third hardest mineral, after diamond at 10 and moissanite at 9.5) – sapphires are also used in some non-ornamental applications, such as infrared optical components, high-durability windows, wristwatch crystals and movement bearings, and very thin electronic wafers, which are used as the insulating substrates of special-purpose solid-state electronics such as integrated circuits and GaN-based blue LEDs. Sapphire is the birthstone for September and the gem of the 45th anniversary. A sapphire jubilee occurs after 65 years.

<span class="mw-page-title-main">Tourmaline</span> Cyclosilicate mineral group

Tourmaline is a crystalline silicate mineral group in which boron is compounded with elements such as aluminium, iron, magnesium, sodium, lithium, or potassium. This gemstone comes in a wide variety of colors.

<span class="mw-page-title-main">Turquoise</span> Opaque, blue-to-green mineral

Turquoise is an opaque, blue-to-green mineral that is a hydrous phosphate of copper and aluminium, with the chemical formula CuAl6(PO4)4(OH)8·4H2O. It is rare and valuable in finer grades and has been prized as a gemstone for millennia due to its unique hue.

Lustre is the way light interacts with the surface of a crystal, rock, or mineral. The word traces its origins back to the Latin lux, meaning "light", and generally implies radiance, gloss, or brilliance.

<span class="mw-page-title-main">Gemology</span> Science dealing with natural and artificial gemstone materials

Gemology or gemmology is the science dealing with natural and artificial gemstone materials. It is a geoscience and a branch of mineralogy. Some jewelers are academically trained gemologists and are qualified to identify and evaluate gems.

<span class="mw-page-title-main">Tanzanite</span> Blue to purple variety of the mineral zoisite

Tanzanite is the blue and violet variety of the mineral zoisite, caused by small amounts of vanadium. Tanzanite belongs to the epidote mineral group. Tanzanite is only found in Simanjiro District of Manyara Region in Tanzania, in a very small mining area approximately 7 km (4.3 mi) long and 2 km (1.2 mi) wide near the Mererani Hills.

<span class="mw-page-title-main">Aventurescence</span> Optical reflectance effect seen in certain gems

In gemology, aventurescence is an optical reflectance effect seen in certain gems. The effect amounts to a metallic glitter, arising from minute, preferentially oriented mineral platelets within the material. These platelets are so numerous that they also influence the material's body colour. In aventurine quartz chrome-bearing fuchsite produces a green stone, and various iron oxides produce a red stone.

<span class="mw-page-title-main">Demantoid</span> Green gemstone variety of the mineral andradite

Demantoid is the green gemstone variety of the mineral andradite, a member of the garnet group of Minerals. Andradite is a calcium- and iron-rich garnet. The chemical formula is Ca3Fe2(SiO4)3 with chromium substitution as the cause of the demantoid green color. Ferric iron is the cause of the yellow in the stone.

<span class="mw-page-title-main">Gemological Institute of America</span> Research institute in Carlsbad, California

The Gemological Institute of America (GIA) is a nonprofit institute based in Carlsbad, California. It is dedicated to research and education in the field of gemology and the jewelry arts. Founded in 1931, GIA's mission is to protect buyers and sellers of gemstones by setting and maintaining the standards used to evaluate gemstone quality. The institute does so through research, gem identification and diamond grading services and a variety of educational programs. Through its library and subject experts, GIA acts as a resource of gem and jewelry information for the trade, the public and media outlets.

<span class="mw-page-title-main">Andesine</span> Silicate mineral comprising 30 to 50 % anorthite and albite

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 and 50%. The formula may be written as Na0.7-0.5Ca0.3-0.5Al1.3-1.5Si2.7-2.5O8.

<span class="mw-page-title-main">Spessartine</span> Nesosilicate, manganese aluminium garnet species

Spessartine is a nesosilicate, manganese aluminium garnet species, Mn2+3Al2(SiO4)3. This mineral is sometimes mistakenly referred to as spessartite.

<span class="mw-page-title-main">Tairus</span>

Tairus is a synthetic gemstone manufacturer. It was formed in 1989 as part of Mikhail Gorbachev's perestroika initiative to establish a joint venture between the Russian Academy of Sciences and Tairus Created Gems Co Ltd. of Bangkok, Thailand. Today Tairus is a major supplier of hydrothermally grown gemstones to the jewellery industry. Later, Tairus became a privately held enterprise, operating out of its Bangkok distribution hub under the trade name Tairus, owned by Tairus Created Gems Co Ltd. of Bangkok, Thailand.

<span class="mw-page-title-main">Moonstone (gemstone)</span> Semi-precious gemstone

Moonstone is a sodium potassium aluminium silicate ((Na,K)AlSi3O8) of the feldspar group that displays a pearly and opalescent schiller. An alternative name for moonstone is hecatolite.

<span class="mw-page-title-main">Adularescence</span> Milky luster or iridescence originating from below the surface of gemstones

Adularescence is an optical phenomenon that is produced in gemstones like moonstone. The optical effect is similar to labradorescence and aventurescence.

Richard T. Liddicoat, Jr. was an American gemologist. Liddicoat was an educator in gemology, who also made contributions in the area of diamond quality grading and gem identification. Liddicoat was the Chairman of the Board of Governors at the Gemological Institute of America (GIA).

<span class="mw-page-title-main">Rainbow lattice sunstone</span> Australian feldspar with geometric inclusions

Rainbow lattice sunstone, also known as rainbow lattice, is a type of orthoclase feldspar that exhibits a rare combination of aventurescence, adularescence, and a distinctive iridescence lattice pattern. The iridescence lattice pattern consists of inclusions that are the result of crystallographically oriented exsolution crystals within the feldspar crystal. Sunstone refers to its physical appearance instead of its chemical composition.


  1. Sunstones at Sunstone Knoll, Millard County. Utah Geological Survey, accessed September 14, 2007.
  2. "Three Occurrences of Oregon Sunstone - Gems & Gemology".
  3. Huges, Richard W. (14 November 2011). "Tibet Andesine Mines; Part 2". RWH Publishing. Retrieved 9 November 2014.
  4. Huges, Richard W. (3 November 2010). "Tibet's Andesine Mines". RWH Publishing. Retrieved 9 November 2014.
  5. Abduriyim, Ahmadjan (10 September 2009). "A Mine Trip to Tibet and Inner Mongolia: Gemological Study of Andesine Feldspar" (PDF). GIA. Retrieved 9 November 2014.
  6. Abduriyim, Ahmadjan (2009). "The characteristics of red andesine from the Himalaya Highland, Tibet". The Journal of Gemmology. 31 (5–8): 134–150. doi:10.15506/JoG.2009.31.5.283.
  7. Abduriyim, Ahmadjan; Kobayashi, Taisuke (2008). Laurs, Brendan M. (ed.). "Gem News International: Visit to andesine mines in Tibet and Inner Mongolia; Gemological properties of andesine collected in Tibet and Inner Mongolia". Gems & Gemology. 44 (4): 369–373. doi: 10.5741/GEMS.44.4.369 .
  8. Hofmeister A.M. and Rossman G.R., 1985, Exsolution of metallic copper from Lake County labradorite: Geology, v.13, p. 644-647.
  9. "Rock Hounding: Oregon Sunstone--Official State Gemstone". Nature of the Northwest. Oregon Department of Geology and Mineral Industries. Archived from the original on 24 April 2015. Retrieved 7 March 2013.
  10. "Chapter 186–State Emblems; State Boundary 2017". Oregon Revised Statutes .

Wikisource-logo.svg This article incorporates text from a publication now in the public domain : Chisholm, Hugh, ed. (1911). "Sunstone". Encyclopædia Britannica . Vol. 26 (11th ed.). Cambridge University Press. p. 110.