Trip to Topaz Mountain
March 28 and 29, 1997
Justin Kreek led Barbara Kreek, Frank Earl, Catherine Quinn, and Catherine's
aunt Lucille Swain on a trip through Topaz Mountain and vicinity on March
28 and 29. The group met around the campfire on Friday night and enjoyed
some-mores, talk, the billions of stars, and the Hale-Bopp comet --- its
two tails shone bright.
After a chilly, but precipitation-free night, we broke camp and looked for
Apache tears in the vicinity. Then it was on to searching for garnets ---
the walk was nice, the garnets few. Lunch and Topaz were the next stop.
Then, it was off to look for a volcanic cone. Half the group made it.
The other group didn't quite get there, but we followed the lava ridge
for a long time on our way to the Pony Express Trail near Simpson Springs.
It was a great trip, and created memories for all.
What Is This Topaz?
Topaz Mountain is the southern extremity of the Thomas Range, a range
composed of rhyolitic lava and volcanic ash. Several eruptive centers in
the area contributed to building the pile of volcanic materials. Later,
gases bubbling up through the cooling lava and ash formed cavities known
as lithophysae, which create the remarkable honey-combed appearance of
some of the rhyolite layers. Within these cavities and along fissures in
the rock, gases and fluids deposited topaz and other minerals.
Topaz can be found throughout the Thomas Range, although only a few areas,
such as Topaz Valley, produce large, clear, well-formed crystals. The
topaz is sherry-colored (orange-brown) when removed from the rock.
Exposure to the sun or to strong lights in a mineral cabinet causes the
color to fade. Crystals that have weathered out of the rock and have been
on the land surface for many years are completely clear and colorless.
The gases and fluids that deposited the minerals did so as they moved
through the rock. If the rock is massive without lithophysae or veins,
then relatively little fluid could have moved through the rock, and topaz
and other minerals are unlikely to be found. The first step, then, is to
look for rock that appears to have had sufficient permeability for fluids
to migrate through it. Much of the rock (but not all of it) in Topaz Valley
is of this type. Secondly, the fluids may have left some sign of their
presence, even if topaz is not immediately evident. The rocks are often
altered to produce seams and pockets of clay; there may be calcite and
fluorite visible; and often the rock is speckled with flakes of hematite.
Sometimes crystals seem to form where two or more veins, fissures, or
layers intersect.
The most highly prized topaz has a deep sherry color, is clear, and has
well-formed crystal faces. Many topaz crystals will have inclusions of
sand (usually quartz) which will lessen their attractiveness and value.
At a few locations, crystals can be found that are totally impregnated
with sand, but still have well-developed crystal terminations.