A Smoky Quartz cabochon from St. Austell, Cornwall, England, UK.

The gem displays an interesting zoned pattern of darker grey areas which penetrate the stone and which follow the hexagonal crystal symmetry of the host Quartz.
These 6-rayed "spokes" are somewhat similar to the trapiche growth features encountered in Emerald and Corundum, as shown in magnified images 4 and 5..

weight:  10.89 carats
shape:   Oval cabochon
dimensions:   16.30 x 12.50 x 7.61 mm
treatment:  None