Pennsylvania State Gemstone
Williamsite STATUS Official DESCRIPTION Williamsite is a translucent to nearly transparent variety of serpentine and a synonym of the mineral antigorite. It occurs in association with magnetite, chrysotile, olivine, and chromite. Chromite is the mineral responsible for williamsite’s color. A magnesium silicate mineral, williamsite is light green to emerald green, blue-green, or white with black crystals often included. Chrysotile and lizardite are closely related members of the serpentine group. STATE SYMBOL Williamsite was first discovered at Woods Chrome, Pennsylvania, in 1849. Today, Line Pit, a chromite mine on the Pennsylvania-Maryland state line, is known for the highest quality williamsite. Mining of chromite, an associate of williamsite and the mineral responsible its color, was an important industry in Pennsylvania in the 19th century. Although williamsite is actually named for Lewis Williams, who first described it, the name calls to mind Pennsylvania’s founder, William Penn. So although Pennsylvania does not have an official state gemstone, williamsite is representative of the state’s geology and history. Lewis W. Williams also first described zaratite (emerald nickel) the same year he described williamsite. NAME ORIGIN Lewis Williams first discovered williamsite at Woods Chrome, Pennsylvania. Antigorite was named for the occurrence at Val Antigorio, Piedmont, Italy. FORMATION AND OCCURRENCE Serpentinite is a major rock-forming mineral. It is found in many igneous and metamorphic rocks, and may be responsible for the color of any green rock. Williamsite commonly replaces rocks that contain iron or magnesium but little or no silica. It forms microscopic masses. GEOGRAPHIC DISTRIBUTION Williamsite is fairly widespread. The following is a list of some localities with well-studied material: Italy: Val Antigorio, Piedmont Austria: Prägraten, Tirol Scotland: Glen Urquhart, Inverness-Shire China: Hsiu-Yen Hsien, Liaoning Province Japan: Nishisonnogi area, Nagasaki Prefecture, and the Sasagure area, Fukuoka Prefecture Australia: Woodsreef, New South Wales United States: Chester and Lancaster counties, Pennsylvania; Baltimore City and Baltimore County, Maryland; Brewster, Putnam County, New York; and Buck Creek, Clay County, North Carolina Canada: Asbestos, Quebec, and Timmins, Ontario USES Williamsite is cut into cabochons and beads for use in jewelry.	Williamsite (Antigorite) Boulder Antigorite with Veins of Asbestos Close-Up of Antigorite SERPENTINE FACTS Group: Serpentine Chemical Formula: (Mg;Fe2+)3Si2O5(OH)4 + or - nH2O Crystal Structure: Monoclinic Hardness (Mohs): 2.5 Color: Yellow, green, brown, black, cream-white Transparency: Translucent to opaque. Rarely transparent. Luster: Greasy, waxy, or silky Pleochroism: None Refractive Index: 1.560-1.571 Density: 2.4-2.8 Streak: White Cleavage: Usually not discernible because of crystal development. Chrysotile may exhibit basal cleavage. Fracture: Conchoidal, splintery
	Some data courtesy of the Mineralogical Society of America Author: World Trade Press