Page 40 - visitorGuide

■ Vanadinite
This specimen of tabular hexagonal crystals of vanadinite comes from Mo-
rocco.The luster of these crystals is typical of vanadinite, which can be bright
red, orange-red, yellow, and brown, with multiple colors showing up in a
single specimen.

In North America, vanadinite is found almost exclusively in
the southwestern United States and Mexico. Unusually
large crystals, up to 1.5 cm, have been mined near
Villa Ahumada, Chihuahua, Mexico.

Vanadinite is used for toughening steel for
use in mechanical parts. It is also used in the
electrical and chemical industries, in printing,
and in the manufacture of ceramics, paints,
and dyes.

Gift from Harold Krueger, Krueger Enterprises, Inc., Cambridge,

Massachusetts.

■ Rhodochrosite Rhodochrosite
Rhodochrosite is a carbonate mineral that is

mined for manganese. When exposed to air, rhodochrosite’s

typical rose-red color can quickly be covered by a crust of black man-

ganese oxide. It is Colorado’s state mineral.

■ Mercury Ore
The polished surface of this specimen, from San Luis Obispo,
California, gives an inner view of a mercury ore composed of
red cinnabar, reddish-black metacinnabar, brassy metallic py-
rite, and lighter colored marcasite. Cinnabar and metacinnabar
are the primary ores of mercury.
Collected and loaned by Edwin B. Eckel, U.S. Geological Survey, Denver, Colorado, and former executive

secretary of the Society.

■ Rock Crystal Quartz
This gem-quality crystal, discovered near Hot Springs, Arkansas, is
nearly flawless. Note the wispy ghosts, or faint parallel growth lines, that
run across the crystal. Crystals like these grow during the cooling of hot,
hydrothermal solutions that have invaded rock fractures and cavities.

Purchased by the Society.

■ Amazonite with Albite, Smoky Quartz, and Goethite
These minerals, from Crystal Park, Colorado (near Pikes Peak), formed mil-
lions of years ago from igneous fluids that solidified into granitic pegmatite
(coarse-grained igneous rock). The blue-green crystals are amazonite. The
thin, white crystals are cleavelandite, a variety of albite often found in pegma-
tites. The elongated, nearly black crystals are smoky quartz. Their dark color
results from exposure to natural radiation. Smoky quartz is frequently found
in pegmatites. The black lumpy masses are goethite, a common iron oxide
mineral.

Gift from Raymond M. Thompson, Englewood, Colorado.

Amazonite

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