This area has been prospected for the industrial commodity perlite,
which here also contains "Apache tears". Perlite is defined as a
hydrated (containing water) volcanic glass with a pearly luster and
concentric "onion-skin" fractures. The "Apache tears" are
unhydrated cores of obsidian (volcanic glass) occurring at the
center of a group of concentric fractures in the perlite. Perlite
often occurs at the chilled margins of rhyolitic (light-colored,
silica-rich) volcanic flows or shallow intrusive rocks, where the
volcanic glass has fractured and allowed meteoric water to enter
the glass structure. The extent of hydration of the glass increases
with temperature; thus the unhydrated "Apache tear" cores represent
the point at which the volcanic rock cooled below the optimum
temperature for hydration to occur.
The light grayish white rock in the cut wall and the "sand"
eroding from it are composed of perlite, which typically contains
2%-6% water. Companies that mine perlite process it by heating the
perlite to high temperatures at which the water in the glass
vaporizes, causing the perlite to "pop" like popcorn. This produces
a product called expanded perlite, with up to 20 times the volume
of the original perlite.
Most expanded perlite is used to make lightweight construction
materials such as concrete and plaster aggregate, acoustical
ceiling tile, and insulation board, but because it is very porous,
it is also used to filter industrial effluent, fruit juices, and
oils. It is used as a soil conditioner to increase drainage and
water retention, and as a filler in paints and an extender in
plastics. The United States is the world's foremost producer of
perlite; most of the mined deposits are located in New Mexico and
other states west of the Rocky Mountains, including Nevada.
According to one legend, the origin of the term "Apache Tears"
for these small obsidian nodules is as follows.
In July 1870, a band of about 75 Apaches responsible for an earlier
raid was surprised by US Calvary troops on a rugged mountain top
overlooking what is now Superior, Arizona. The outnumbered Apache
warriors who escaped the initial volley of gunfire deliberately
jumped off the steep cliff face of the mountain to their deaths.
The bereaved families and friends of the Apache braves later
gathered at the base of the cliffs and mourned for days following
the tragedy. Legend is that their tears turned into stone upon
hitting the ground and the translucent gray to black nodules of
obsidian found nearby are commonly called Apache Tears. The place
in Arizona where this occurred is now known as Apache Leap
Mountain.
TO LOG THIS EARTHCACHE, POST A PHOTO OF THE SITE ON THE CACHE
WEBPAGE AND ANSWER THE FOLLOWING QUESTIONS: WHAT IS THE DIAMETER OF
THE LARGEST APACHE TEAR YOU CAN FIND HERE? IS IT CLOSEST TO:
A) 1 MILLIMETER
B) 5 MILLIMETERS
C) 1 CENTIMETER
D) 3 CENTIMETERS
E) 10 CENTIMETERS
AND WHAT IS THE LONGEST DIMENSION OF THE EXCAVATED AREA AT THE
PROSPECT? IS IT CLOSEST TO:
A) 5 METERS
B) 10 METERS
C) 50 METERS
D) 100 METERS
E) 500 METERS
