Amethyst — specimen 0678, photo © NMNHS
Weight: 0.56 ct; size: 6.25 | 5.39 | 3.96 mm; shape: hexagon; colour: light violetish blue; strong; clarity: eye clean; cut: excellent; treatment: none.
Very clean specimen; design ‘Hexamixtum S 41-32’ [pavilion angle changed to 45.00], 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.