Here's a pair of champagne zircons I cut for someone who fossicked them in Australia. She wanted the largest pair I could get out of both--for a bypass ring though, not earrings. I told her I'd shoot for 6mm x 4mm if I could, and they finished at 6.01 x 3.98 and 6.02 and 4.01. Nailed it!
5mm dot grid paper, no filters used. Diffuse daylight.
(sorta prompted by @Justanotherpiercer)
@arctangent these are lovely!! And such a rare colour Zircon to see!!!