Ch. 16: Gemstone Definitions, Values, Imports, ... Collections of Gems

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	318	GEMS AND PRECIOUS STONES IN THE

	to the light, they form perfect mirrors. All the specimens are brilliant in color and rival any work ever done in hard material. One of the finest sections of an agatized trunk was sent to New York in the autumn of 1888. It measured 40-1/2 by 34 inches on the top, was 36 inches high, and weighed 2-1/2 tons. The top was four months undergoing the process of grinding down and polishing; it is a deep, rich red, yellow, black, mottled and variegated, and beautifully polished. This is probably the finest piece of hard-stone polishing that has been done in the United States. The company has removed from the forest 180 tons of material, and 20 tons of sections have been ground down to show its characteristic beauty. The process is briefly as follows : The faces of the rough sections are irregular, and must be worn down to a smooth surface. To accomplish this they are set in circular form in what is known as the " Drake Beds," about ten feet in diameter, composed of various-sized sections of the material set by the use of a spirit level, in order to secure an even face. They are then cemented together, and large slabs of Sioux Falls quartzite are attached to two arms of a powerful vertical shaft These large, flat stones, which are almost as hard as the silicified wood and extend the full length of the arms, are revolved about the bed by a stream of water, with crushed quartzite reduced to the size of a pea. The silicified wood, being tougher than quartzite, soon wears grooves in these large stones, which are frequently reversed, and sometimes discarded for new ones. This initial stage of the work continues for nearly forty hours, when the quartzite stones are replaced by large sections of the silicified trees, which have been previously worn upon the bed, and these are revolved sometimes for one week, sometimes for two weeks, and fed with sand of quartzite until, by abrasion rather than cutting, a face is disclosed on the bed, which, for the first time, indicates the true colorings and quality of the material. From these beds, each of which requires about thirty horse-power when doing the best work, the specimens are taken up, and re-bedded on a car thirty feet long and eight feet wide. The success of the operation depends upon the exactness of face of the different pieces. This car moves by cogs and concentric rings, the outermost of which is six feet in diameter, revolving at forty revolu-

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