English

Noun

positive crystal ‎(plural positive crystals)

1. (optics) 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, such as as quartz and ice; as opposed to negative crystal: one in which this characteristic is reversed, such as Iceland spar or tourmaline.

Antonyms

• negative crystal