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Ch. 10: Chiastolite, Cyanite, Datolite, Staurolite, ... Fluorite

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180
GEMS AND PRECIOUS STONES IN THE
crystals, 1/10 to 1/4 inch in length, lining cavities of what is called "mahogany ore," a dark-brown, compact mixture, consisting prin­cipally of limonite and oxide of copper in varying proportions.1 It has since been found in larger and finer crystals, but notwith­standing its rich emerald-green color, its softness prevents its use as a gem. These crystals are not equal to those from the Khir-ghesse Steppes, Siberia. Single crystals from there are occasion­ally mounted entire without cutting.
Prehnite has been found in a number of localities in the United States, and gems have been cut from material found at Bergen Hill and Paterson, N. J. It is a stone of rich, oily-green
PREHNITE
color, generally in botryoidal sheets or spheres. Quite a number of these, some an inch in diameter, were found at the Pennsylvania open cut, and in the cutting of the Morris and Essex Tunnel through Bergen Hill, N. J. When cut and polished, it resembles Chrysoprase in color and lustre. Zonocholrite, chlorastrolite, and lintonite have been referred to this species, but Dr. George W. Hawes found by analysis that they were only impure varieties.
Zonochlorite was described by Prof. A. E. Foote in 1873, and was obtained by him in 1867 on a small island off Neepigon Bay, north shore of Lake Superior, where it occurs associated with quartz, amethyst, carnelian, etc. The largest pieces found are less than 2 inches across. Its hardness varies from 6-5 to 7. It received
1 Am. J. Sci., III., Vol. 23, p. 325, April, 1882·
Ch. 10: Chiastolite, Cyanite, Datolite, Staurolite, ... Fluorite Page of 364 Ch. 10: Chiastolite, Cyanite, Datolite, Staurolite, ... Fluorite
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