Amethyst — specimen 0199, photo © NMNHS
Weight: 2.83 ct; size: 9.16 | 9.15 | 6.36 mm; shape: octagon; colour: medium dark violetish blue; strong; clarity: eye clean; cut: excellent; treatment: none.
Very clean specimen; design ‘Eight’ by Glenn & Martha Vargas, excellent cut by Tan Pen.
More information from ‘Classification’
A violet variety of quartz. The colour is caused by iron impurities in the 10s to 100s parts per million range.