Gem-quality red beryl from the Wah Wah Mountains, Utah.

Abstract

Prismatic crystals of red beryl up to several centimetres in greatest dimension occur in fractures and other cavities within a Tertiary volcanic rhyolite. They have epsilon 1.564-1.569, omega 1.568-1.574; pleochroism epsilon purplish-red, omega orange-red to red; sp.gr. 2.66-2.70; a 9.229-9.234, c 9.204-9.212 A. Chemical analyses are given for the rim and core zones of a colour-zoned crystal, and 20 minor and trace elements also detected are recorded in ppm. Absorption spectra exhibit bands at 425, 480, 530, 560 and 810 nm. The beryl is thought to have been deposited by a high-T gas or vapour phase released during the late stages of crystallization of the host rhyolite.-R.V.D.