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The property of crystallizing under two or more distinct fundamental forms, including dimorphism and trimorphism.

The property possessed by some substances of crystallizing in closely similar forms while unlike in chemical composition.

A crystalline substance said to be found in the root of a certain plant of the Leadwort (Plumbago) family.

ch receives and polarizes the light. It is usually a reflecting plate, or a plate of some crystal, as tourmaline, or a doubly refracting crystal.

Manganese dioxide, occurring in tetragonal crystals nearly as hard as quartz.

A substance capable of crystallizing in several distinct forms; also, any one of these forms. Cf. Allomorph.

nd in the bark of certain species of the poplar (Populus), and extracted as a sweet white crystalline substance.

Relating to, or resembling, porphyry, that is, characterized by the presence of distinct crystals, as of feldspar, quartz, or augite, in a relatively fine-grained base, often aphanitic or cryptocrystalline.

to designate a rock consisting of a fine-grained base (usually feldspathic) through which crystals, as of feldspar or quartz, are disseminated. There are red, purple, and green varieties, which are highly esteemed as marbles. Porphyry shell (Zoöl.), a handsome marine gastropod shell (Oliva porphyria), having a dark red…

not acid; -- opposed to negative, and said of metals, bases, and basic radicals. Positive crystals (Opt.), a doubly refracting crystal in which the index of refraction for the extraordinary ray is greater than for the ordinary ray, and the former is refracted nearer to the axis than the latter, as quartz and ice; -- op…

rbonate obtained by leaching wood ashes, either as a strong solution (lye), or as a white crystalline (pearlash).

A variety of cryptocrystalline of a leek-green color.

oat at or near the surface. Red precipitate (Old. Chem), mercuric oxide (HgO) a heavy red crystalline powder obtained by heating mercuric nitrate, or by heating mercury in the air. Prepared in the latter manner, it was the precipitate per se of the alchemists. -- White precipitate (Old Chem.) (a) A heavy white amorpho…

A pale green mineral occurring in crystalline aggregates having a botryoidal or mammillary structure, and rarely in distinct crystals. It is a hydrous silicate of alumina and lime.

Pertaining to, or designating, a tetrabasic acid of benzene obtained as a white crystalline substance; -- probably so called from the resemblance of the wartlike crystals to the mammillæ on the surface of prehnite.

A defect of vision consequent upon advancing age. It is due to rigidity of the crystalline lens, which producepresbytia.

mary rocks (Geol.), a term early used for rocks supposed to have been first formed, being crystalline and containing no organic remains, as granite, gneiss, etc.; -- called also primitive rocks. The terms Secondary, Tertiary, and Quaternary rocks have also been used in like manner, but of these the last two only are no…

all the inclosed spheres with their planets in a daily revolution from east to west. See Crystalline heavens, under Crystalline. The motions of the greatest persons in a government ought to be, as the motions of the planets, under primum mobile. Bacon.

through the point of sight perpendicular to the perspective plane. -- Principal section (Crystallog.), a plane passing through the optical axis of a crystal.

Same as Orthorhombic. Prismatic borax (Chem.), borax crystallized in the form of oblique prisms, with ten molecules of water; -- distinguished from octahedral borax. -- Prismatic colors (Opt.), the seven colors into which light is resolved when passed through a prism; primary colors. See Primary colors, under Color.…