Facetdial

Facetdial keeps light inside the stone. Pick a species or type a refractive index and it returns the critical angle, the pavilion main it implies with a safe margin, a suggested crown angle, and a plain verdict on whether the angle you plan to cut will leave a window.

Fourteen species carry refractive index, hardness, cleavage warnings and typical angles — including the awkward ones like fluorite, where the maths bites. Eight cutting designs list facet counts, index gear and difficulty, and you can save any of them with your own angle tweaks.

The stone log records rough and finished weight, design, angles cut and dop method, and computes yield per stone plus your average and best.

A machine reference covers dop transfer, index setting, mast height and polishing agents, with a lap-grit progression and a safety screen on wet grinding, cleavage and thermal shock. Offline, nothing leaves the device.