Oregon produces some of the best gem-quality feldspar in the world. The name "Oregon Sunstone" is
used for gem-quality feldspars from Oregon, with and without aventurescence. They can be found in colors that
range from clear through yellow, orange, pink, red, green and blue. Multiple colors are often found in the
same crystal, making bicolor and tricolor stones possible.
Some specimens of Oregon Sunstone contain microscopic copper platelets suspended throughout the material. These platelets
are often in alignment within the stone and light entering the stone at the proper angle will simultaneously reflect
from them. When these stones are played in the light a bright copper-colored flash is produced as the stone passes
through the angle of reflection. Flashes can also be observed by moving the light source or changing the angle
of observation. This interaction with the light produces the phenomenon known as aventurescence.
Sunstone is cut into faceted stones and cabochons. Material with platelets is usually cut to produce flashes of light
when the stone is viewed in the face-up orientation. To do this the copper platelets should be parallel to the top and
bottom of the stone. Quality material cut by a skilled artisan is so attractive that the State Legislature named
Oregon Sunstone the State's official gemstone.
The sunstones are found as phenocrysts in a small number of basalt flows. This makes production a labor-intensive job.
They can be screened by hand from soils which have developed above the basalts. Hardrock mining of the basalt is
sometimes done but it is less successful because the feldspar cleaves easily and breaks during extraction.
>> Places where you can find rocks & gems in Oregon <<
The most popular rock in Oregon is said to be the "thunderegg". Thundereggs are "nodules" or "geodes" that form
when agate, chalcedony or opal precipitates within the cavities of rhyolite, welded tuff or perlite. They are ugly on the
outside; however, when they are cut or broken open a treasure of colorful gem material and crystals is often revealed. Thundereggs range in size
from less than one inch to over three feet in diameter.
The mystery of breaking or sawing thundereggs to see what is inside is a large part of what makes them so popular. They frequently
contain layered or fortification patterns of colorful agate, sometimes with a drusy quartz-lined inner cavity. Other specimens
contain clear to milky or mossy chalcedony.
Opal: Precious, Fire and Common
A number of different types of opal are found in Oregon. An area known as Opal Butte in Morrow County has produced hyalite,
hydrophane, crystal, contra luz, fire, common, dendritic and other varieties of opal. Although some of the opal found there is unstable
during cutting a number of great gemstones are still produced.
A small fraction of Oregon thundereggs are filled with opal. A small fraction of those contain gem-quality material with play
of color. Some contain a blue opal known as Owyhee Blue that ranges from a blue gray to a brilliant sky blue. The hope of
finding opal is part of what drives the thunderegg popularity.
Agates, Jasper and Wood
The volcanic history of Oregon has produced a wide variety of agates and jaspers. Famous Oregon agates include: Graveyard Point, Priday,
and Polka Dot. Famous Oregon jaspers include Biggs, Deschutes, and Sucker Creek. A favorite place to find agates is along Oregon's
many beaches. Agates found on beaches are often nicely rounded and can quickly be brought to a polish in a rock tumbler.
Contributor: Hobart King
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|Two pieces of Oregon Sunstone. The specimen on the left is a faceted stone weighing 1.01 carat and 7mm x 5mm in size. It is an oval shaped stone with a strong orange color. The specimen on the right is a cabochon weighing 2.29 carats and 7mm in size. It is a round stone that is heavily included with visible platelets of copper.|
|Examples of thundereggs sawn to display their interior. The top two are halfs of a single egg about three inches in diameter. It is filled with gray chalcedony with gray agate and druzy quartz in the center. . The bottom is a half egg about six inches in diameter with gray banded agate around the outside, white agate towards the center and a druzy quartz cavity in the center.
|A faceted orange fire opal from Oregon. This stone weighs 1.17 carats and is 9mm x 7mm in size. Fire opal in a range of colors from yellow through orange and red is produced from several mines on the eastern side of the Oregon Cascades.|
|A cabochone cut from blue Owyhee opal mined in the Owyhee Mountains in eastern Oregon near the Oregon-Idaho border. Opal from this area looks like chalcedony and occurs in a range of pale blue to medium blue colors. This stone is 20mm x 11mm in size and weighs 8.05 carats.|