Amethyst — specimen 0228, photo © NMNHS
Weight: 3.50 ct; size: 9.95 | 9.92 | 6.60 mm; shape: octagon; colour: light bluish violet; very slightly greyish; 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.