Page 35 - visitorGuide

■ Chrysotile Asbestos
Asbestos is not the name of a specific mineral—it is a commercial term for a
group of silicate minerals that readily separate into thin, strong fibers that are
flexible, heat resistant, and chemically inert. Chrysotile and tremolite are two
minerals that were commonly used in asbestos. Asbestos was widely used in
a variety of industrial products, though rarely now because asbestos has been
found to be carcinogenic.This specimen is from Salt River Canyon, Arizona.
Gift from Harrison Cobb, Boulder, Colorado.

■ Polished Serpentinite Spheres
Serpentine is a soft, massive metamorphic rock. It is composed mainly of

two serpentine minerals, antigorite and chrysotile. Serpentine, frequently
used as a decorative rock, has slick, smooth surfaces. Seams and veins of
fibrous chrysotile are mined for use in fireproof materials. Serpentine gets

its name from the “snakeskin” appearance of sleek, greasy, multicolored
serpentinite rock surfaces.
From Williams Quarry, Easton, Pennsylvania; shaped by B.F. Shepherd, Ingersoll-Rand Co. Gifts from Lafayette
College, Easton, Pennsylvania, through Arthur Montgomery and Paul J. Roper, in honor of Lafayette alumnus
Edwin B. Eckel.

■ Siderite with Goethite
Siderite is a minor ore of iron. Its shiny brown, reddish brown, gray, or white
crystals often are curved. Siderite becomes black and magnetic when it is
heated. In this specimen, goethite has formed as an alternation product on
the bladed siderite crystals. It may be from the Gilman mining district in Eagle
County, Colorado, where siderite is common in masses and as a lining in cavi-
ties in the rocks.

Siderite forms in a variety of environments. It forms masses or concretions
in clay, coal seams, and shale. It occurs with sulfide minerals in hydrothermal
veins with silver, lead, and copper ores. It is found as a replacement deposit
in limestones that have been altered by iron-bearing solutions. It is also found
in a few igneous rock types including pegmatite. Siderite gets its name from
the Greek sideros (“iron”).

Deep Sea Drill Core

■ Deep Sea Drill Core
This section of drill core was collected during the Deep Sea Drilling Project
at Site 169 southwest of Hawaii at latitude 10°40.2′N, longitude 173°33.0′E. It
was recovered in 5407 m (17,740 ft) of water at a depth of 187 m (614 ft) below
the sea floor.The dark igenous rock solidified from magma with high iron and
manganese content. This rock intruded into Cretaceous sedimentary layers
that were deposited at the bottom of the ocean.
Permanent loan from the National Science Foundation, through W.R. Riedel, curator, Deep Sea Drilling Project.

■ Fulgurite
This rock was formed when a 50,000-volt power line fell apart during a storm
near Gold Hill, west of Boulder, Colorado. The electricity flowed through the
wet grus (crumbly decomposed granite) and fused it. The white chunks are
pieces of feldspar, one of the main minerals of granite. Fulgurites are usually
formed by lightning.
Gift from Mary C. Eberle.

25GARDEN LEVEL EXHIBITS