Sunstone

Sunstone
Sunstone
General
Category Crystal
Chemical formula sodium calcium aluminum silicate (Ca,Na)((AI,Si)2Si2O8)
Identification
Color clear, yellow, red, green, blue, and copper shiller
Crystal habit Euhedral Crytals, Granular
Crystal system Triclinic
Twinning Lamellar
Cleavage 001 Perfect, 010 Good
Fracture Conchoidal
Mohs scale hardness 6–7.2
Luster Vitreous
Streak white
Diaphaneity Transparent to Translucent
Density 2.64–2.66
Optical properties Double Refractive: weak to medium
Refractive index 1.525–1.58
Dispersion Weak

Sunstone is a plagioclase feldspar, which when viewed from certain directions exhibits a brilliant spangled appearance; this has led to its use as a gemstone. It has been found in Southern Norway, and in some United States localities. It is the official gemstone of Oregon.

Contents

Properties

Unpolished sunstone

The optical effect appears to be due to reflections from inclusions of red copper, 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 called shiller and the color in Oregon Sunstone is due to copper. In the middle part of this crystal, it sparks a lot, and usually has a dark color in the middle, and the color becomes lighter as it becomes the outer part.

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."

Distribution

Sunstone was not common until recently. 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. Due to the discovery of large deposits in Oregon, Sunstone is now readily available.

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

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]

Oregon sunstone

Various gem colors of Oregon sunstone

A variety known as Oregon sunstone is found in Harney County, Oregon and in eastern Lake County north of Plush. Only Oregon sunstone contains inclusions of copper crystals.[2] Oregon sunstone can be found as great as three inches wide. 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.[3]

On August 4, 1987, Oregon State Legislature designated Oregon sunstone as its state gemstone by joint resolution.[4][5]

References

  1. ^ Sunstones at Sunstone Knoll, Millard County. Utah Geological Survey, accessed September 14, 2007.
  2. ^ McClellan, Jan. Oregon Sunstone, Fact and Fancy. Designer Jewelry.
  3. ^ Oregon Sunstone - Official State Gemstone. Nature of the Northwest: Rock Hounding, accessed September 13, 2007.
  4. ^ Chapter 186 – State Emblems; State Boundary 2005 Oregon Revised Statutes
  5. ^ "Oregon Symbols". SHG Resources. http://www.shgresources.com/or/symbols/gemstone/. Retrieved 2007-09-14. 

 This article incorporates text from a publication now in the public domainChisholm, Hugh, ed (1911). Encyclopædia Britannica (11th ed.). Cambridge University Press. 

External links



Wikimedia Foundation. 2010.

Игры ⚽ Нужна курсовая?

Look at other dictionaries:

  • Sunstone — Sun stone , n. (Med.) Aventurine feldspar. See under {Aventurine}. [1913 Webster] …   The Collaborative International Dictionary of English

  • sunstone — /sun stohn /, n. a reddish variety of oligoclase feldspar, used as a gem, having a red and bright yellow play of color. [1350 1400; ME; see SUN, STONE] * * * ▪ mineral       a gemstone variety of feldspar that has minute platelike inclusions of… …   Universalium

  • sunstone — avantiūrinas statusas T sritis chemija apibrėžtis Kvarco atmaina su fuksito, hematito ir kitų mineralų intarpais. atitikmenys: angl. aventurine; sunstone rus. авантюрин; солнечный камень ryšiai: sinonimas – Saulės akmuo …   Chemijos terminų aiškinamasis žodynas

  • Sunstone Magazine — is a publication by the Sunstone Education Foundation, Inc., a 501(c)(3) nonprofit corporation, that discusses Mormonism through scholarship, art, short fiction, and poetry. The foundation began the publication in 1974 and considers it a vehicle… …   Wikipedia

  • Sunstone Knoll — Bild gesucht  BWf1 Höhe 1.412  …   Deutsch Wikipedia

  • Sunstone Circuits — is a Printed circuit board (PCB) manufacturer founded in 1972 and located in Mulino, Oregon, just outside of Portland. The current CEO is Terry Heilman. Sunstone claims their quick turnaround for prototype or relatively smaller orders of PCB s is …   Wikipedia

  • sunstone — noun A translucent form of feldspar having flakes of hematite, used as an ornamental stone …   Wiktionary

  • sunstone — noun a chatoyant gem consisting of feldspar, with a red or gold lustre …   English new terms dictionary

  • sunstone — /ˈsʌnstoʊn/ (say sunstohn) noun aventurine felspar …  

  • sunstone — noun a translucent quartz spangled with bits of mica or other minerals • Syn: ↑aventurine • Hypernyms: ↑quartz, ↑transparent gem • Hyponyms: ↑goldstone …   Useful english dictionary

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”