Page 41 - visitorGuide

■ Tennanite Crystals on White Drusy Quartz
This specimen, from Chihuahua, Mexico, features dark tennanite crystals
scattered across a white quartz slab. Tennanite is an important copper ore
mineral and is named for English chemist SmithsonTennant (1761–1815).

Gift from Raymond M. Thompson, Englewood, Colorado.

■ Smoky Quartz with Topaz
This specimen is made up of smoky quartz and yellow to-
paz. Smoky quartz, or cairngorm, ranges from pale smoky

brown to almost black.The topaz fromTeofilio, Brazil, is a
hard mineral that forms in certain igneous and metamor-
phic environments. In addition to yellow, topaz can be
colorless or shades of white, blue, green, brown, violet,
pink, and red. Gem-quality topaz is found in the Pikes
Peak region.

Gift from Raymond M. Thompson, Englewood, Colorado.

Smoky Quartz with Topaz ■ Malachite and Limonite
In this specimen from Bisbee, Arizona,

bright green malachite encrusts massive

brown limonite. Malachite is copper ore and is valued as an or-

namental stone and gemstone. It takes its name from the Greek

moloche (“mallow”) for its typical grass-green to emerald-green

color. Limonite is an ore of iron found in shades of yellow, brown,

or black. It is used in paints and pigments. Limonite is named from

the Greek leimons (“meadow”).

Gift from the Geology Museum, Colorado School of Mines, Golden, Colorado.

■ White Celestite Crystals with Native Sulfur
This group of white celestite crystals and yellow native sulfur crystals are
from Agrigento, Sicily. Celestite, sulfur, and salts are often found together
in layered evaporite deposits.

Gift from Raymond M. Thompson, Englewood, Colorado.

■ Sand-Barite Roses
Sand-barite roses, or “desert roses,” are Oklahoma’s official state rock. Their
roselike appearance is due to naturally grown clusters of sandy barite crys-
tals that develop when barium-rich groundwater moves through sand-rich
rocks or layers. The rosettes, from central Oklahoma, inherited their red
color from the ancient red sandstones in which they grew. The sand-barite
roses are harder than the rock they formed in, so they are left behind when
the rock around them is exposed at Earth’s surface and weathers away.

The sand-barite rosettes of Oklahoma occur mostly in Garber Sandstone,
which was deposited during the Permian Period, about 250 million years ago.
The area just east of Norman is particularly renowned for its abundant and
well-formed specimens.

Gift from the Oklahoma Geological Survey, courtesy of Kenneth S. Johnson.

■ Magnetite in Metamorphosed Limestone
This specimen is from the Cornwall iron mine once in central Pennsylvania.
This mine was closed at the end of 1972 after 230 years of continuous opera-
tion. The specimen is an aggregate of magnetite crystals (iron oxide) and a
group of crystals of analcite.

Gift from Bethlehem Steel Corporation, through Gilbert L. Hole.

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