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agate
(Encyclopedia)agate ăgˈĭt [key], translucent, cryptocrystalline variety of quartz and a subvariety of chalcedony. Agates are identical in chemical structure to jasper, flint, chert, petrified wood, and tiger's-e...moss agate
(Encyclopedia)moss agate: see agate.mocha stone
(Encyclopedia)mocha stone: see agate.Agate Fossil Beds National Monument
(Encyclopedia)Agate Fossil Beds National Monument: see National Parks and Monuments (table)national parks and monuments (table). ...onyx
(Encyclopedia)onyx ŏnˈĭks [key], variety of cryptocrystalline quartz, differing from agate only in that the bands of which it is composed are parallel and regular. Its appearance is most striking when the bands ...chalcedony
(Encyclopedia)chalcedony kălsĕdˈənē [key] [from Chalcedon], form of quartz the crystals of which are so minute that its crystalline structure cannot be seen except with the aid of a microscope. Chalcedony has ...quartz
(Encyclopedia)quartz, one of the commonest of all rock-forming minerals and one of the most important constituents of the earth's crust. Chemically, it is silicon dioxide, SiO2. It occurs in crystals of the hexagon...Scottsbluff
(Encyclopedia)Scottsbluff skŏtsˈblŭfˌ [key], city (1990 pop. 13,711), Scotts Bluff co., W Nebr., on the North Platte River near the Wyo. line; inc. 1900. It is the market, distribution, and processing point of ...Petrified Forest National Park
(Encyclopedia)Petrified Forest National Park, 93,533 acres (37,881 hectares), E Ariz.; est. as a national monument 1906, designated a national park 1962. A part of the Painted Desert, it contains the largest known ...month
(Encyclopedia)month, in chronology, the conventional period of a lunation, i.e., passage of the moon through all its phases. It is usually computed at approximately 29 or 30 days. For the computation of the month a...Browse by Subject
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