Access to this location is off of the Rainbow Gardens Road, reached
from Lake Mead Boulevard. You will need a 4-wheel drive vehicle
with good tires, and this is reflected in the terrain rating. A
tape measure or ruler will also be needed to measure veins of
gypsum at this site.
Gypsum is a soft mineral composed of hydrated calcium sulfate,
and is formed through a process called evaporative deposition. In
this process, salts precipitate out of very concentrated solutions
and settle to the bottom of the lake or sea in which they are
formed. Most of the gypsum found in this area is in the form of
selenite crystals, which formed within clay lenses. Gypsum found
near Las Vegas is thought to have formed in both marine
environments (such as the Blue Diamond gypsum deposit), and desert
playa lakes (as in the PABCO deposits to the northeast of
here).
At this location, the Rainbow Gardens Road passes through a wash
in which several veins of gypsum have been exposed. Concrete was
placed in the wash to slow erosion, but as you can see, the force
of water during flow events has just gone around the concrete and
increased the erosion by eating away the gypsum.
South of this location, on the Rainbow Gardens Road, is evidence
of the White Eagle Gypsum Mine, an early Las Vegas area gypsum
mining concern. The gypsum beds in this area are from the
Miocene-aged Horse Spring Formation (5-10 million years old), and
the Triassic-aged Moenkopi Formation (about 240 million years
old).
When you reach the coordinates for this Earthcache, park your
vehicle at the edge of the road and walk down the wash. The gypsum
veins are identified by being the white, crystalline material in
the bottom of the wash. Using your measuring tape or ruler, measure
the width of 10 of the gypsum veins.
To receive credit for this Earthcache, send me an email with the
answers to the following questions: 1.) What is the average width
of the gypsum veins in this wash? 2.) What do you think is the
purpose of the rock which is piled about 300’ to the south of
this location?
In addition, take a picture with you and your GPS receiver with
Rainbow Gardens in the background. Post your picture with your log
when you log your find.
The above information was compiled from the following sources:
Beffort, B. 2006. Afoot and Afield Las Vegas & Southern
Nevada.
Castor, B.S., and Ferdock, G.C. 2003. Minerals of Nevada. Online
at: (visit link)
Tingley, J.V. et al. Geologic Tours in the Las Vegas Area.
Nevada Bureau of Mines and Geology Special Publication 16.
