Geology Reference
In-Depth Information
amount of copper in the stone, ranging from a low of
20 parts per million for yellow to 200 parts per million
for red. Heliote is a calcium-rich variety of plagioclase
feldspar known as labradorite. It occurs as large crystals
in basalt from 4 small localities in Oregon, all of which
are privately owned except for one locality in Lake
County on Bureau of Land Management lands. Here
these gems are referred to as "Plush diamonds" because
of the nearby town of Plush. In Harney County near
Hines, the sunstones are being mined in commercial
amounts by private companies. Some of the stones are
priced over $1000 per caret.
Geothermal Resources
The Basin and Range is a region of high
temperature gradients, numerous faults, and volcanic
activity which make it a province of intense geothermal
phenomena. Because heat flow varies considerably from
place to place as it moves through the earth's interior,
higher temperatures are found in the mountains, while
lower temperatures characterize the valleys here.
Geothermal sources result when groundwater, flowing
along fault zones, encounters rocks which are abnor-
mally hot. Using the faults as conduits, the heated
waters often reach the surface as hot springs.
The area around around Vale, the Alvord
Desert, Lakeview, and Warner Valley have characteris-
tically high heat flow records. The Vale hot springs
vicinity has a particularly high potential for geothermal
resources. In this zone of thermal activity, surface and
near surface springs and hot water wells have a temper-
ature range as high as 200 degrees Fahrenheit. South
of Vale along the Owyhee River canyon, natural
mineral springs with waters up to 120 degrees Fahren-
heit form a pool that is used by the public for bathing.
Along with the Vale region, the Alvord Valley
is thought to have significant geothermal potential.
Several thermal springs emerge south of Alvord Lake
along the north-south Steens fault zone. One of these,
Borax or Hot Lake, is a large pool 800 feet across
formed by discharging water with a temperature of 97
degrees Fahrenheit. The water contains borax salts
which have built up a low, mile-wide dome. It has been
estimated that water from two of the largest springs
here deposits enough salts to produce 150 tons of boric
acid a year. In the late 1800s the land and springs were
purchased for $7000, and the 20-Mule Team Borax
Company, later called the Rose Valley Borax plant,
began to mine and remove the borax. For 10 years
borax was taken out to the railhead at Winnemucca,
Nevada, with wagons drawn by teams of mules. Borax
operations ceased by 1902, but ruins of the old build-
ings can still be seen.
On the extreme northern edge of the Alvord
An assortment of freshwater diatoms from within
the Klamath Basin (photo Oregon Dept. Geology
and Mineral Industries)
Diatomite
Diatomite, bentonite, and zeolite minerals are
all exploited in small amounts from the eastern region
of the Great Basin province. Diatomite deposits in the
Juntura and Otis basins are the remains of microscopic
siliceous skeletons of diatoms, single-celled aquatic
plants that accumulated in a former freshwater lake.
Typically white in color, the diatomite beds here range
from a few inches to 20 feet in thickness within the
Miocene Juntura and Drewsey formations. First mined
between 1917 and 1934 and again commencing in 1986,
diatomite is used as an absorbent cat box filler and as
a filter for chemicals and drinking water.
To the southeast, bentonite (volcanic ash) and
zeolites are produced from localities in Malheur
County near the Idaho border. Mined from within the
Miocene Sucker Creek Formation, high-swelling
bentonies are utilized primarily as a sealant in dams,
landfills, and waste sites. Small amounts of potassium-
rich zeolites from the same formation were first
extracted in 1975, but commercial markets for this
mineral have developed only slowly. Currently zeolites
are used as carriers for agricultural chemicals.
Sunstone
One of the most outstanding minerals of semi-
precious quality is the state gem, the heliote or sun-
stone, a clear feldspar that varies in color from yellow
or red to green and blue. The color relates to the
