Amethyst — specimen 0733, photo © NMNHS
Weight: 24.52 ct; size: 22.73 | 19.25 | 13.63 mm; shape: oval; colour: light bluish violet; very slightly greyish; clarity: eye clean; cut: excellent; treatment: none.
Very clean specimen; design ‘Ovalimixtum’ [crown angle changed to 42.00], 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.