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tourmaline
(Encyclopedia)tourmaline to͝orˈməlĭn, –lēn [key], complex borosilicate mineral with varying amounts of aluminum, iron, magnesium, sodium, lithium, potassium, and sometimes other elements, used as a gem. It o...Wilson, Benjamin
(Encyclopedia)Wilson, Benjamin, 1721–88, English portrait painter and electrician who opposed Benjamin Franklin's theory of positive and negative electricity. Instead, Wilson supported Newton's gravitational-opti...cat's-eye
(Encyclopedia)cat's-eye, gemstone that displays a thin band of reflected light on its surface when cut as a cabochon. Its name is derived from its supposed resemblance to the eye of a cat. The optical effect, known...Aepinus, Franz Ulrich Theodosius
(Encyclopedia)Aepinus, Franz Ulrich Theodosius fränts o͝olˈrĭkh tāˌōdōˈzēo͝os âpēˈno͝os [key], 1724–1802, German physicist. He studied at Jena and Rostock and taught mathematics at Rostock from 174...polarization of light
(Encyclopedia)polarization of light, orientation of the vibration pattern of light waves in a singular plane. Unpolarized light can be converted into a single polarized beam by means of the Nicol prism, a device ...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...boron
(Encyclopedia)boron bōrˈŏn [key] [New Gr. from borax], chemical element; symbol B; at. no. 5; interval in which at. wt. ranges 10.806–10.821; m.p. about 2,300℃; sublimation point about 2,550℃; sp. gr. 2.3 ...sand
(Encyclopedia)sand, rock material occurring in the form of loose, rounded or angular grains, varying in size from .06 mm to 2 mm in diameter, the particles being smaller than those of gravel and larger than those o...gem, ornamental mineral or organic substance
(Encyclopedia)gem, commonly, a mineral or organic substance, cut and polished and used as an ornament. Gems also are used as seals (items of assurance) and as talismans (good-luck charms). For birthstones, see mont...Browse by Subject
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