TOPAZ AT HONEYCOMB HILLS, JUAB COUNTY, UTAH: EVIDENCE OF PEGMATITIC TOPAZ FROM THE 4.7MA ERUPTION AT HONEYCOMB HILLS
The four crystals were determined to be topaz. They are different when compared to the vapor phase topaz from Topaz Mountain, also in Juab County, Utah. Topaz Mountain, a 6-7 ma rhyolite, yields beautiful vapor phase, transparent amber colored topaz with perfect crystal faces, unlike the crystals found at Honeycomb Hills. The amber color in these crystals is sensitive and the crystals will turn clear when exposed to sunlight, whereas, the crystals at Honeycomb in the stream bed were constantly being exposed to sunlight but they still retain their color.
The three crystals ranged in size from 8mm to 15mm across at the widest section. The largest crystal is translucent and displays perfect cleavage, and although it’s been etched and weathered, the crystal faces and its orthorhombic shape are still present; the termination of this crystal is covered with tiny crystals. The yellow and green topaz do not look like the vapor phase Topaz Mountain crystals; their appearance is similar to topaz found in pegmatites.
The smallest of the three crystals found at Honeycomb Hills was made into a thin section and analyzed by the scanning electron microscope (SEM) where many trace elements were found in this specimen including a few rare earth elements (REEs), Ho, Y, and U, and other transition metals Zr, Nb, Hf, Ta, Cr, and Te. Further analysis of these specimens includes more thin sections, SEM analyses, and x-ray diffraction. The purpose of this research is to better understand the topaz found at the Honeycomb Hills site in Juab County, Utah.