Williamsite
is a translucent, pale,
apple green to intense, chrome green variety of
Antigorite that gets its color from the presence of
chromium (Cr) in its chemistry. It often contains inclusions of dark, octahedral microcrystals
of Chromite.
Williamsite from some localities has a jade-green color
and has been used as a Jade simulant. Williamsite
has a Mohs hardness of 3.5 - 4.0 and a vitreous to resinous
luster. Antigorite
is a member of the Serpentine
Group of minerals that
also includes Chrysotile
and
Lizardite.
Williamsite
was named in 1848 by American mineralogist
Charles Upham Shepard
(1804-1886) in honor of its discoverer, Lewis
White Williams (1804-1873), a mineralogist and geologist of West Chester, Chester County,
Pennsylvania.
Williamsite
originally came from the historic State Line Chrome
Mine which lies just inside Lancaster County, Pennsylvania on
the Pennsylvania-Maryland border. This mine was active
from the 1800's into the early 1900's. Williamsite has
also been found at Wood's Chrome Mine, Texas, Little Britain Township, Lancaster County, Pennsylvania, USA.
However, as of Summer 2012, the property and mine are closed to collectors.
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