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Ch. 6: Aquamarine

Ch. 6: Aquamarine Page of 515 Ch. 6: Garnet Text size:minus plus Restore normal size   Mail page  Print this page
246
A POPULAR TREATISE ON GEMS.
color of hyacinth is preferable to that of zircon ; a carat of the former is worth from fifteen to twenty dollars. Zircon is imitated by pastes, which may easily be detected by their lustre, hardness, and specific gravity; burnt topaz may be substituted for it.                                         
The jargon is a variety of zircon, being composed of the same constituents, and differing merely in color from the first. It is mostly of white, grayish-white, and greenish-white colors, with tinges of green, blue, red, and yellow; but generally of a smoky white color. It usually occurs in worn angular pieces, or in small, detached crystals, of an octahedral form. The crystals are smooth, and of a bright adamantine lustre; have a conchoidal fracture, and double refraction; seldom quite transparent; is harder than quartz, and of a specific gravity of 4.3 ; loses its color when ex­posed to the blowpipe flame, but is infusible. It oceurs chiefly in the sand of a river in Ceylon, accompanied by sapphire, spinelle, tourmaline, &c.
On account of its peculiar adamantine lustre, it has often been substituted for the diamond, and a century ago it was regarded as an inferior variety of the true diamond, and few of the precious stones were in more request, especially for mourning ornaments, for which the dark tone of its color, combined with its lustre, was supposed peculiarly appro­priate. It has no value, at present, in market, although it is still seen in the cabinet and in the collections of jewellers.
Hyacinth differs from jargon and zircon only in color, being of a red orange color, very bright and transparent; it is much more employed for. setting than zircon. It occurs also in the sand and alluvial deposits of some rivers in Ceylon ; at Espaillie, near Puy> in France; at Ohlapian, in Transylvania; occasionally in volcanic tufa, in Auvergne, and at Vesuvius. Siberia affords crystals as large as-wal-
Ch. 6: Aquamarine Page of 515 Ch. 6: Garnet
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