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Oregon Sunstone

Filed under: Mineral of the day,Rare Rocks!,Video — Gary October 31, 2010 @ 10:49 am

world’s largest  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. Oregon sunstone can be found as large as three inches across. The copper leads to varying color within some stones, where turning one stone will result in multiple colors. The more copper within the stone, the darker the complexion.

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

Oregon sunstone

Oregon Sunstone

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.

The optical effect appears to be due to reflections from enclosures of red haematite, in the form of minute scales, which are hexagonal, rhombic or irregular in shape, and are disposed parallel to the principal cleavage-plane. These enclosures give the stone an appearance something like that of aventurine, whence 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.

Sunstone Mining

Sunstone Mining

Sunstone

Sunstone

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.

unpolished_sunstone

Unpolished 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.

n the short video below you will see the process of prospecting for Oregon sunstone with the use of a drill. As drilling begins we watch the cuttings coming out of the hole. With experience you can tell when it is time to check the cuttings more closely. The drilling penetration rate will vary depending on the type of material being drilled. The color and size of the particles will also vary.The bore hole is cleaned out by compressed air. Compressed air is pumped down the inside of the drill pipe and through the bit. The cuttings are blown to the surface and caught by hand for examination. If you are drilling in a potential mining site there will be ground up particles of feldspar in the cuttings. When you find feldspar in the cuttings you note how much drill pipe is in the hole being drilled. This will tell you how deep to dig with heavy equipment. The video will give you a better understanding and appreciation of what it is like to prospect for sunstone.

Thanks Wikipedia

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