Abstract

Frankdicksonite, BaF2, occurs in small quartz veinlets in the Carlin gold deposit, Eureka County, Nevada. It is of hydrothermal origin, and the only closely associated mineral is quartz. The mineral crystallizes with the fluorite structure, with space group Fm3m,a = 6.1964 ± 0.0002 Å, and V = 237.91 ± 0.03 Å3. Strongest X-ray powder diffraction lines and their relative intensities are 3.581 (100), 2.191 (56), and 1.870 (47). Chemical analysis by electron microprobe gave Ba 77.98, Sr 0.24, F 21.41, sum 99.63 wt percent; spectrographic analysis showed Si 0.02, Al <0.002, Fe <0.001, Mg 0.0015, Ca <0.001, Ba Major, Cu <0.0007, Sr 0.5. Formula unit Ba0.995Sr0.005F2 Z = 4. Frankdicksonite occurs as small transparent euhedral crystals which are vitreous in luster, show {100} growth faces, and perfect {111} cleavage. Vickers hardness on {111} cleavage faces varied from 88-94 kg/mm2 and averaged 90 (10 determinations). Density measured is 4.89 ± 0.01, calculated density is 4.885 g cm−3. The mineral is isotropic with index of refraction n = 1.475 ± 0.001 measured in sodium light at 20°C. Under electron bombardment the mineral shows a strong medium-blue cathodoluminescence. The name frankdicksonite isin honor of Dr. Frank W. Dickson, Professor of Geochemistry. Stanford University.

This content is PDF only. Please click on the PDF icon to access.

First Page Preview

First page PDF preview
You do not currently have access to this article.