. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. 522 REPORT OF NATIONAL MUSEUM, 1900. Quartz iiu-ludes a larger number of kinds of gems among its varie- ties than any other mineral. The varieties arise from differences in color, mode of formation, or (nystallization. These varieties, though differing wideh' in appearance and passing uifder a variety of names, are chemically all of one sul)stance. The following is a list of the kinds commonly recognized: Agate.—A variegated chalcedonic qua
. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. 522 REPORT OF NATIONAL MUSEUM, 1900. Quartz iiu-ludes a larger number of kinds of gems among its varie- ties than any other mineral. The varieties arise from differences in color, mode of formation, or (nystallization. These varieties, though differing wideh' in appearance and passing uifder a variety of names, are chemically all of one sul)stance. The following is a list of the kinds commonly recognized: Agate.—A variegated chalcedonic quartz, the colors in clouds, spots, bends, or layers. The bands or layers may be either parallel or concen-. Fig. 9. AGATIZED WOOD. Chalcedony Park, Arizona. .Specimen No. 82485, trie, and either in straight, circular, or zigzag forms. Banded agates may be called fortification^ handed., or eye agates^ according to the arrangement of the layers, (See fig. 8.) Agatized 'wood.—\\oo([ siliciried by silica and usually having the structure of the original material. The western part of the United States affords some remarkal)le specimens of this material. In Apache County, Arizona, there is a silicitied forest in which trunks 150 feet. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Smithsonian Institution. Board of Regents; United States National Museum. Report of the U. S. National Museum; Smithsonian Institution. Report of the Secretary. Washington : Smithsonian Institution
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