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GEM-STONES
Peridots of deep bottle-green hue command moderate prices at the present day, about 30s. a carat being asked for large stones; the paler tinted stones run down to a few shillings a carat. The rate per carat may be very much larger for stones of exceptional size and quality.
Olivine, to use the ordinary mineralogical term, is a common and important constituent of certain kinds of igneous rocks, and it is also found in those strange bodies, meteorites, which come to us from outer cosmical space. Except in basaltic lavas, it occurs in grains and rarely in well-shaped crystals. Stones that are large and transparent enough for cutting purposes come almost entirely from the island Zebirget or St. John situated on the west coast of the Red Sea, opposite to the port of Berenice. This island belongs to the Khedive of Egypt, and is at present leased to a French syndicate. It is believed to be the same as the mysterious island which produced the ‘topaz’ of Pliny’s time. Magnificent stones have been discovered here, rich green in colour, and 20 to 30, and occasionally as much as 80, carats in weight when cut; a rough mass attained to the large weight of 190 carats. Pretty, light-green stones are supplied by Queensland, and peridots of a less pleasing dark-yellowish shade of green, and without any sign of crystal form, have during recent years come from North America. Stones rather similar to those from Queensland have latterly been found in the Bernardino Valley in Upper Burma, not far from the ruby mines.
CHAPTER XXVI
ZIRCON
(Jargoon, Hyacinth, Jacinth)
ZIRCON, which, if known at all in jewellery, is called by its variety names, jargoon and hyacinth or jacinth, is a species that deserves greater recognition than it receives. The colourless stones rival even diamond in splendour of brilliance and display of ‘fire’; the leaf-green stones ([Plate XXIX], Fig. 13) possess a restful beauty that commends itself; the deep-red stones ([Plate XXIX], Fig. 14), if somewhat sombre, have a certain grandeur; and no other species produces such magnificent stones of golden-yellow hue ([Plate XXIX], Fig. 12). Zircon is well known in Ceylon, which supplies the world with the finest specimens, and is highly appreciated by the inhabitants of that sunny isle, but it scarcely finds a place in jewellery elsewhere. The colourless stones are cut as brilliants, but brilliant-cut fronts with step-cut backs is the usual style adopted for the coloured stones.
Zircon is a silicate of zirconium corresponding to the formula ZrSiO4, but uranium and the rare earths are generally present in small quantities. The aurora-red variety is known as hyacinth or jacinth, and the term jargoon is applied to the other transparent varieties, and especially to the yellow stones. The most attractive colours shown by zircon are leaf-green, golden-yellow, and deep red. Other common colours are brown, greenish, and sky-blue. Colourless stones are not found in nature, but result from the application of heat to the yellow and brown stones.