Amethyst — specimen 0415, photo © NMNHS
Weight: 0.67 ct; size: 6.64 | 5.63 | 4.01 mm; shape: oval; colour: medium bluish violet; slightly greyish; clarity: eye clean; cut: excellent; treatment: none.
Very clean specimen; design ‘Ovalimixtum ST’, 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.