The Tank Creek troctolite-dunite massif occupies an area of about 2 sq.km and is composed of slightly serpentinized dunite with veins of troctolite.
In the anorthosite deposits, gray and gray-blue opaque corundum
prevails.Pink and red corundum, sometimes translucent and partially transparent, is rare. Cuttable rubies
are recovered from 2 to 10-carat prismatic and tabular crystals and aggregates. Gemstones of one carat or less have been cut from such raw material. Some corundums are colour-zoned.
crystals were first found in North Carolina at the end of the 19th century. Since that time, several small deposits have been discovered. They all contain rare gem quality emeralds, but are largely a source of crystals for collectors.
in North Carolina are generally related to granite pegmatites.
Ref: E.Ya. Kievlenko, Geology of gems, 2003, pp. 60, 77
Gem list contains entries from all listed localities in region.
Localities in this Region