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polymorphism

(Encyclopedia)polymorphism, of minerals, property of crystallizing in two or more distinct forms. Calcium carbonate is dimorphous (two forms), crystallizing as calcite or aragonite. Titanium dioxide is trimorphous;...

pyroxene

(Encyclopedia)pyroxene pīˈrŏksēn [key], name given to members of a group of widely distributed rock minerals called metasilicates in which magnesium, iron, and calcium, often with aluminum, sodium, lithium, man...

melamine

(Encyclopedia)melamine mĕlˈəmēnˌ [key], common name for 2,4,6-triamino-1,3,5-triazine. Melamine is a trimer (see polymer) of cyanamide, H2NC≡N, and is synthesized from calcium carbide. It condenses with form...

grease

(Encyclopedia)grease, mixture of lubricant and thickener. It is used to reduce friction between surfaces from which oils would leak away or cause damage by dripping, or where lubrication must be assured for extende...

amphibole

(Encyclopedia)amphibole ămˈfəbōlˌ [key], any of a group of widely distributed rock-forming minerals, magnesium-iron silicates, often with traces of calcium, aluminum, sodium, titanium, and other elements. The ...

teff

(Encyclopedia)teff, annual plant, Eragrostis tef, of the grass family (Poaceoe), whose seeds are a staple grain in Ethiopia and Eritrea. It is a gluten-free cereal grain, high in iron, protein, calcium, vitamin C, ...

fluorite

(Encyclopedia)fluorite flo͞oˈərspär [key], mineral appearing in various colors, e.g., green, yellow-brown, rose, and red. Chemically, it is calcium fluoride, CaF2. Its crystals, commonly cubic, are transparent ...

alizarin

(Encyclopedia)alizarin əlĭzˈərĭn [key], or 1,2-dihydroxyanthraquinone, mordant vegetable dye obtained originally from the root of the madder plant (Rubia tinctorum), in which it occurs as a glucoside. The term...

vegetable

(Encyclopedia)vegetable, term originally used for any plant, now the name for many food plants, most of them annuals, and for their edible parts. There is no clear botanical distinction between vegetables and fruit...

spectroheliograph

(Encyclopedia)spectroheliograph, device for photographing the surface of the sun in a single wavelength of light, usually one corresponding to a chief element contained in the sun, e.g., hydrogen or calcium; the re...