Ch. 1: Diamonds

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	UNITED STATES, CANADA AND MEXICO	27

	edges, the convex faces, and the solid angles are caused by an apparently secondary building up of the faces of a perfect octahedron, and for the same reason the girdle is not a perfect square, but has a somewhat circular form. These observations were well shown by enlarged drawings. The faces seem to be composed of thin plates overlying each other, each slightly smaller than the last. These plates are triangular, but the lines forming the triangles are curved, and the edges of the plates are beveled. Mr. Hanks remarked that it could be seen by the enlarged crystals shown under the microscope, and by drawings exhibited, that each triangular plate was composed of three smaller triangles and that all the lines were slightly curved. The building up of plate upon plate caused the channeled edges and the somewhat globular form of this exquisite crystal. A close examination of the crystal revealed tetrahedral impressions, as if the corners of the minute cubes had been imprinted on the surface of the crystal while in a plastic state. These are the result of the law of crystallography, as was shown by the faint lines forming a lace-work of tiny triangles on the faces when the stone was placed in a proper light. Mr. Hanks concluded with the remark that it would be an act of vandalism to cut this beautiful crystal, which is doubly a gem, and he protested against its being defiled by contact with the lapidary's wheel. The Cherokee district, in Butte County, has been, from as early as 1853, one of the most prolific diamond localities in the State. Cherokee is near the North Fork of Feather River, and the geological relations of the diamonds and gold are essentially the same as those in Amador County, a hundred miles to the northwest, both districts lying among the western foot-hills of the Sierras, as previously described. Mr. Hanks calls attention to included leaf-impressions in the volcanic beds, as proving them to be tufas and not lavas. In number, the Cherokee diamonds obtained are about equal to those from Volcano. One was shown by Professor Silliman, on the occasion already mentioned, in 1867 ; and others were then known to be from that locality. William Bradreth obtained a crystal in the same year which he afterward had cut into a fine white stone of 1-3/16 carats. In 1873, several were obtained from the ground of the Spring Val-

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