positive crystal

positive crystal

[′päz·əd·iv ′krist·əl]
(optics)
Uniaxial anisotropic crystal having the ordinary index of refraction greater than the extraordinary index.
Biaxial anisotropic crystal having the intermediate index of refraction beta closer in value to alpha, and with Z the acute bisectrix.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
Mentioned in ?
References in periodicals archive ?
Needle-like positive crystals (type III) are observed if crystallization occurs at 300 [degrees] C.