flat plate-glass exhibition-cases, the gems being neatly marked with printed labels, and arranged on velvet pads with a silk-rope border. The diversity, brilliance, and richness of Nature's brightest colors displayed render the whole effect a very attractive and pleasing one. The collection begins with a suite of glass models of the historical diamonds, followed by a series of diamonds in their natural state, among which is an interesting octahedron, eighteen carats in weight.[1] These specimens are good illustrations of the form from South Africa, though of little commercial value as gems. One dozen other crystals from one quarter to one carat in weight complete a representative set of form and occurrence in that region. Next we have a very neat set of a dozen more crystals, small but choice, principally from India and Brazil, and formerly belonging to the Mallet collection. One of these is a perfect cube, a form peculiar to Brazil, while another is twinned parallel to the octahedron. Another stone of one carat is only half cut, and for comparison we have a stone of about the same weight completely cut.
Among the sapphires we find a carat, oblong stone of dark-blue color, from the Jenks mine, Macon County, North Carolina, which has yielded a few fair sapphires, yellow, violet, and blue, and a few rubies, some of the finest of which were in the Leidy collection; also the first stones found here, the dark-brown, asteriated sapphires, described in "Transactions of the New York Academy of Sciences," March, 1883, and two other cut stones weighing from four to eight carats. These all show a slight bronze play of light on the dome of the cabochon in ordinary light, but under artificial light they all show well defined stars, being really asterias or star-sapphires, and not cat's-eyes, as would seem at first glance. There are also two cut stones, light blue and light green, weighing one and two carats respectively, which, for light-colored sapphires, are perhaps, when cut, brighter than those from any other locality. The cutting of one of these gems has given it a remarkable luster. They are found in the sluice-boxes at and near Helena, Montana. Following are two broken crystals of the dark green sapphires from the quite recent find at the Hills of Precious Stones in Si am, beautifully dichroitic, being green and blue when viewed in different axes. An asteria of good blue color, measuring nearly one inch across, a beautiful two-carat ruby-asteria, and a small three-quarter-carat ruby, of fair color, complete the corundum gems
- ↑ Gems are generally bought and sold by the weight, called a carat, which is equal to about 3·168 troy grains. It is usually divided, however, into four diamond or pearl grains, each of which is ·7925 of a true grain. Fractions of a carat are also known as fourths, eighths, sixteenths, thirty-seconds, and sixty-fourths. The weight of the carat formerly differed slightly in different countries, and this diversity finally led a syndicate of Parisian jewelers, goldsmiths, and gem-dealers, in 1871, to propose a standard carat. This was subsequently confirmed by an arrangement between the diamond-merchants of London, Paris, and Amsterdam, fixing the uniform value of the diamond (?) carat at ·205 grain.
