Columbia Encyclopedia
Search results
70 results found
flint, mineral
(Encyclopedia)flint, variety of quartz that commonly occurs in rounded nodules and whose crystal structure is not visible to the naked eye. Flint is dark gray, smoky brown, or black in color; pale gray flint is cal...abrasive
(Encyclopedia)abrasive, material used to grind, smooth, cut, or polish another substance. Natural abrasives include sand, pumice, corundum, and ground quartz. Carborundum (silicon carbide) and alumina (aluminum oxi...topaz
(Encyclopedia)topaz tōˈpăz [key], aluminum silicate mineral with either hydroxyl radicals or fluorine, Al2SiO4(F,OH)2, used as a gem. It is commonly colorless or some shade of pale yellow to wine-yellow; pale bl...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...sandpaper
(Encyclopedia)sandpaper, abrasive originally made by gluing grains of sand to heavy paper sheets. Today sandpaper is made primarily with quartz, aluminum oxide, or silicon carbide grains, and is graded according to...schist
(Encyclopedia)schist shĭst [key], metamorphic rock having a foliated, or plated, structure called schistosity in which the component flaky minerals are visible to the naked eye. Schists are distinguished from the ...geode
(Encyclopedia)geode jēˈōd [key], hollow, globular rock nodule ranging in diameter from 1 to 12 in. (2.54–30.5 cm) or more. Most geodes are partly filled with mineral matter; they have a thin layer of chalcedon...Goiás
(Encyclopedia)Goiás goi-äsˈ [key], state, 211,941 sq mi (548,927 sq km), central Brazil. Goiânia is the capital. The ...Atlin Lake
(Encyclopedia)Atlin Lake ătˈlĭn [key], long, irregular mountain lake, c.300 sq mi (780 sq km), NW British Columbia, Canada, touching the Yukon boundary. It is the source of the Yukon River. The town of Atlin is ...carboloy
(Encyclopedia)carboloy kärˈbəloi [key] [portmanteau word from carbon and alloy], an alloy containing cobalt, tungsten, and carbon. This alloy is extremely hard, harder than steel; it is used to cut steel, porcel...Browse by Subject
- Earth and the Environment +-
- History +-
- Literature and the Arts +-
- Medicine +-
- People +-
- Philosophy and Religion +-
- Places +-
- Africa
- Asia
- Australia and Oceania
- Britain, Ireland, France, and the Low Countries
- Commonwealth of Independent States and the Baltic Nations
- Germany, Scandinavia, and Central Europe
- Latin America and the Caribbean
- Oceans, Continents, and Polar Regions
- Spain, Portugal, Italy, Greece, and the Balkans
- United States, Canada, and Greenland
- Plants and Animals +-
- Science and Technology +-
- Social Sciences and the Law +-
- Sports and Everyday Life +-
