EPA 2014c), was the site of a former mine that produced vermiculite contaminated with a mixture of asbestiform amphiboles, including winchite, richterite
, and tremolite asbestos (Meeker et al.
The studied volcanic outcrops are constituted by lamproites composed by forsteritic olivine, Ti phlogopite, diopside, enstatite, richterite
with Ti and K, leucite, and Fe-rich sanidine.
Geological Survey (USGS), which worked in conjunction with the EPA at the Libby site, 95 percent of the amphiboles from the samples were winchite and richterite
, neither of which has ever been classified as asbestos.
However, at T > 950[degrees]C instead of layered hectorite a needle-like richterite
The hornblende-plagioclase thermometry actually consist of two reactions, the A thermometer uses the edenite-tremolite reaction (edenite + 4 quartz = tremolite + albite, in quartz rich rocks) and the B thermometer uses the edenita-richterite
reaction (edenite + albite = richterite
+ anorthite) (Holland and Blundy, 1994).
Amphibole forms of asbestos are often divided into those with considerable commercial exploitation (amosite and crocidolite) and those that are encountered largely as intrusions into other mineral deposits (tremolite, actinolite, anthophyllite); thus, tremolite is found in many chrysotile ore beds, and an amphibole that has been variously labeled as tremolite, richterite
, or winchite is found in vermiculite ore from Libby, Montana.
Calcite lenses in high-grade metamorphic rocks at this site gave up the richterite
crystals when Laurent Thomas came by about five years ago with his digging equipment; at Munich, eight of the crystals were available (see Laurent's website for Polychrom Minerals at www.
Abdel-Rahman (2006) analysed amphiboles from analogous but a little younger (Cambrian) peralkaline granite in Egypt and found here also mainly arfvedsonite (as we in Socotra) together with richterite
which we did not found in our samples.
In contrast, Libby amphibole is a mixture of six amphiboles, mostly winchite (84%), richterite
(11%), and tremolite (6%), including prismatic crystals, acicular fragments, and bundles of fibrils approximately 100 nm to 1 [micro]m in diameter with lengths up to 20 [micro]m (Meeker et al.
The major component species are forsterite, phlogopite, diopside, richterite
, chromite and pyrite, and some of the lamproites of the Kimberley area also contain some very rare species, including priderite, jeppeite and wadeite (Grice and Boxer, 1990).
Libby amphibole asbestos was determined to be composed of tremolite, winchite, and richterite
(Meeker et al.
However, Dudley Blauwet's three crystals were carefully identified as richterite
by amphibole expert Frank Hawthorne, a sufficienfly authoritative source to be considered definitive.