Quarterly Crystal: Topaz with Phlogopite
This issue’s quarterly crystal is a gem-quality very light pinkish brown topaz (figure 1) from the Dusso mine in Pakistan. The transparent singly terminated topaz crystal measures 30.52 × 29.84 × 27.89 mm and weighs 216.56 ct. It hosts a prominent 6 mm long dark brownish orange phlogopite mica booklet that shows strong brownish orange and yellow dichroism as well as lamellar cleavage planes (figure 2).
Figure 2. This prominent 6 mm crystal of phlogopite mica is hosted by the Pakistani topaz. Photomicrograph by Nathan Renfro; field of view 9.09 mm.
A tiny cluster of dark brownish red manganotantalite and colorless albite inclusions are also present. Small near-colorless and transparent mica and feldspar inclusions are randomly scattered throughout the crystal. This suite of inclusions strongly suggests that a complex granitic pegmatite was the parent rock type of this topaz.
