Page 33 - visitorGuide

■ Galena Crystals
Galena is the most common of the lead minerals. It frequently contains
enough silver to be mined as a silver ore, too. Soft and heavy, it is dark lead-
gray with a metallic luster. It typically takes the form of cube-shaped crystals.

These large cubic galena crystals, from the Royal Flush mine, Socorro
County, New Mexico, were deposited from mineralizing fluids that moved into
limestone layers through fractures and fault zones. The limestone has been
partially altered to clay minerals.The clear stubby crystals are smoky quartz.

In addition to being a source of lead, galena has been used as the radio
crystal in crystal-detector radio receivers.
Gift from James McGlasson, Colorado School of Mines, Golden, Colorado.

■ Silicified Wood
This specimen, from the Upper Cretaceous Wayan Formation

in Wayan, Idaho, is a cross section through the trunk of a gi-
ant tree fern, Tempskya. The tree ferns grew to several
meters (10–12 ft) in height, with trunks up to 40 cm (16
in) in diameter. The internal structure of the plant is
well preserved.
Gift from the Department of Geology, Idaho State University, Pocatello,
through H. Thomas Ore.

■ Malachite on Native Copper
This specimen is made up almost entirely

of native copper, but was covered with a
thin coating of green malachite and oth-

er minerals when the copper oxidized.
Gift from William J. LeVeque, Claremont, California.

■ Copper Dragon
This fine cluster of native crystalline
copper is thinly coated with the red-
brown dust of cuprite (copper oxide).
The blue-green color is a mixture of
other copper minerals. To some, the
specimen appears to resemble a dragon. The specimen
is from the South Pit, Chino mine, Santa Rita, New Mexico, known for ruby
red cuprite crystals scattered across native copper.
Gift from Gregory E. McKelvey, Bear Creek Mining Company, Tucson, Arizona.

■ Linarite on Fluorite
Deep blue linarite crystals and gray fluorite crystals form this rock from Blan­
chard mine in Socorro County, New Mexico. Some samples of linarite fluo-
resce.The word “fluorescence” is derived from fluorite’s characteristic violet-
blue luminescence under ultraviolet light. Fluorescent minerals emit light
when exposed to ultraviolet light of certain wavelengths.These minerals glow
in the dark under black light. Their luminescence is caused by the motion of
electrons in their atomic structures—the minerals absorb energy from light.
The absorbed energy temporarily boosts electrons in the minerals to higher
energy levels. As the electrons return to their normal energy levels, the extra
energy is released in the form of light. Linarite is named for its discovery site
near Linares, Spain.

23GARDEN LEVEL EXHIBITS