THE GEOLOGY
The geologic history of the area is interesting. About 380
million years ago, the African Continent was being forced toward
the Ancestral Eastern North American Continent by plate tectonic
force. The subduction, or forcing down of the Oceanic Crust
underneath the North American Continent produced tremendous
friction-generated heat from the two colliding continents.
This friction-generated heat in excess of 2,000 degrees
Fahrenheit melted the surrounding rock 9 to 15 miles below the
surface. This igneous molten rock was generated under intense
pressure that forced the molten rock into cracks and fissures of
preexisting rock. This molten rock under pressure is similar to hot
hydraulic fluid being forced into a chamber. Due to the pressure
exerted on the molten fluid, it hydraulically pushed its way
through the cracks of the host rock. This opened the rock up, along
with melting contact areas of the host rock and sucking up rich
mineral forming fluids. As these cooled, they crystallized and
became a mineral-rich buried treasure.
It then took an estimated 100 million years for this deeply
buried (and insulated) mass to cool and crystallize. The slowly
cooling mineral crystals grew within the area to some of the
largest feldspar and mica crystals in the world. After molten
emplacement and cooling, it took millions of more years of
Appalachian Mountain building and subsequent erosion to expose the
deposits we see today.
Along with muscovite mica, feldspar (plagioclase), perthite, and
quartz occur at the Ray Mica mine. Other minerals reported are
golden and aquamarine beryl, apatite crystals, clear oligoclase
(plagioclase feldspar), amazonite, thulite, garnet, autunite,
columbite-tantalite, tourmaline, zircon and rutile.
AREA HISTORY
The story of prospecting and mineral production in the area
began before recorded time when the “Ancients” mined for glittering
mica during the Woodland age 2000 years ago. The Ancients, an early
name given to the Native Americans by settlers of the area, mined
mica for grave decoration and wampum which they traded as money.
The mica is known to have been traded as far away as the Ohio
Valley and is believed to have originated from Native American
mines in the Spruce Pine/Burnsville area now known as the Clarissa,
Ray, and Sinkhole mines. Legend is that this mining of mica led
Hernando DeSoto to the area around 1540 in search of mineral wealth
that he thought to be gold and silver. He found only silver mica
better known as muscovite mica.
Later, around 1744, legend is that Cherokee Indians mined
semi-weathered feldspar, mica and kaolin from the Spruce Pine
pegmatites and used oxen-drawn sleds to transport it to the coast
where it was loaded on ships bound for England. In England, it was
used as an ingredient for patented English ceramic wares.
From 1767 to 1911, mining of feldspar and mica occurred
sporadically. Mica was mined to fuel the demand for the
newly-developed Edison electric motor in 1878. The motor required
the electrical insulating properties of sheet mica. Feldspar and
mica were being hand-mined at hundreds of holes, pits, and mines
throughout Mitchell, Avery, and Yancey Counties, which make up the
Spruce Pine Mining District.
Until the mid- to late-1940s, most work, especially ore
separation of minerals, was done by hand with crude machinery and
hand tools. Between 1944 and 1949, the process of chemical
separation of minerals was jointly developed by the Feldspar Mining
Company, the North Carolina Feldspar Corporation, the Tennessee
Valley Authority, and the North Carolina State Mineral Research
Laboratory of Asheville. This process led to the current large
volume, high-capacity process of separating the minerals of
feldspar, mica, quartz, and garnet from the rock (ore).
TODAY'S USES
Mica comprises about 10% of the rock mass in
the area. Once highly valued for wood- and coal-burning stove
windows (often called "isinglass") and for radio tube
insulators during both world wars, it is now used as an
industrial products special additive.
Muscovite, which is silver to white mica variety, is mostly
ground to a fine particle size. It is valued for its flat particle
shape. It is used mostly as a major ingredient of drywall joint
compound or sheet rock joint cement. Muscovite’s flat particle
shape and light color allow it to serve as an anti-shrinking agent
for the cement after it is applied to sheet rock joints. It applies
as smooth, damp putty, but because of muscovite mica’s flat
particle shape, it interlocks the mud as it dries, therefore
reinforcing the mud as it dries, without shrinkage. It also acts as
a fire retardant within the sheet rock joint.
Mica is also produced for use as special electrical insulators,
automobile metallic flake paint, women’s make-up, and as a
reinforcing additive in special plastics and paints. It is used in
oil well drilling fluids to seal and lubricate the bore hole during
drilling.
Be aware that the listed coordinates will bring you near a
relatively deep mica shaft! Though it is fenced off you should be
careful while in the area!! There are many shafts in the area so
watch your step!!!
In order to fulfill the requirements for this Earthcache you
must do three things:
1. Estimate the depth of the shaft located at
the listed coordinates and email this distance to me. (Click
here.) [See the top photo.]
2. Load a photo to your online log of your GPSr next to a decent
size chunk of mica. You should be able to find mica just about
anywhere along the trail and/or near the listed coordinates. [See
the middle photo.]
3. Load a photo to your online log of you and/or your group with
the Ray Mine Road sign in the background. The sign is located at N
35° 53.377 W 82° 16.912. [See the bottom photo.]
Parking is available at N 35° 53.244 W 82° 16.708. Enjoy your
time in the area!
FTF HONORS GO TO
Konnarock Kid & Marge!!!
[And to Streetdoc, who sort of found it
retroactively.]
