~~~ in the field is to hold them up to light (sunlight or lamp) and look for light passing through; especially in the ring(s) which are the weakest point of the chip.since ivory turners kept that ring location in the exact distance from the edge on both sides which were prone to hairline fractures while in rough play which can and has led to a much longer fracture; the same as to what happens in a windshield from a pebble chip. Also, sometimes those fractures are filled in with crayon or some form of filler which can easilly be detected (shrinkage).

The area (rings) which are most vulnerable to fracture.