sunstone

sunstone

[suhn-stohn]
noun
a reddish variety of oligoclase feldspar, used as a gem, having a red and bright-yellow play of color.

Origin:
1350–1400; Middle English; see sun, stone

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World English Dictionary
sunstone (ˈsʌnˌstəʊn)
 
n
another name for aventurine
 
[C17: so called because it contains red and gold flecks which reflect the light]

Collins English Dictionary - Complete & Unabridged 10th Edition
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Encyclopedia Britannica
Encyclopedia

sunstone

a gemstone variety of feldspar that has minute platelike inclusions of iron oxide (hematite or goethite) oriented parallel to one another throughout. The reflections from these inclusions give the mineral (usually the plagioclase feldspars albite, oligoclase, or labradorite, but sometimes the alkali feldspar orthoclase) a spangled appearance and often a reddish glow. The stone is often cut en cabochon (i.e., with a rounded and convex polished surface). Sunstone occurs in Tvedestrand, Nor.; near Lake Baikal, Russia; and at Middletown, Pa., and Statesville, N.C., in the United States.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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