Asbestos Fibers and Other Elongate Mineral Particles: State of the ...

Table 1. Definitions of general mineralogical terms (Continued)
144
Glossary of Geology, 5th ed.
[American Geological
Institute 2005] Leake et al. [1997] NIOSH [1990a]
Dictionary of Mining,
Mineral, and Related
Terms [U.S. Bureau
of Mines 1996]
[Note: Footnotes identify the Primary
Source Citation for the definition]
Term
a generic term for a large group of
white or colorless (sometimes tinted
red or yellow by impurities) hydrous
aluminosilicate minerals that have
an open framework structure of
interconnected (Si,Al)O4 tetrahedra with
exchangeable cations and H2O molecules
in structural cavities. They have a ratio
of (Al + Si) to nonhydrous oxygen of 1:2,
and are characterized by their easy and
reversible loss of water of hydration and
by their ready fusion and swelling when
strongly heated under the blowpipe.
Zeolites have long been known to occur as
well formed crystals in cavities in basalt.
Of more significance is their occurrence
as authigenic minerals in the sediments
of saline lades and the deep sea and esp.
in beds of tuff. They form “during and
after burial, generally by reaction of
pore waters with solid aluminosilicate
materials (e.g., volcanic glass, feldspar,
biogenic silica, and clay minerals).” 8
Zeolite 1. A generic term for class of
hydrated silicates of aluminum
and either sodium or calcium
or both, of the type Na2O. Al •
2O3.nSiO2 xH2O. The term
originally described a group of
naturally occurring minerals.
The natural zeolites are analcite,
chabazite, heulandite, natrolite,
stilbite, and thomsonite.
Artificial zeolites are made
in a variety of forms, ranging
from gelatinous to porous and
sandlike, and are used as gas
adsorbents and drying agents
as well as water softeners. Both
natural and artificial zeolites
are used extensively for water
softening. The term zeolite now
includes such diverse groups
of compounds as sulfonated
organics or basic resins, which
act in a similar manner to effect
either cation or anion exchange.
See footnotes at end of table. (Continued)
NIOSH CIB 62 • Asbestos