Originally Posted by dcg
It was my understanding that that's the argument currently being used against synthetic sapphire - the lab made variety is only distinguishable because those made in a lab are flawless, whereas there will always be small flaws in natural stones. Can anyone confirm/deny?
Originally Posted by West24
not true at all. many made in a lab will react different in different tests. i.e. high fluoresence when tested under UV light etc. and they arent always flawless, many times they will have flux, or feathers or certain growing plates. it also matters how they were lab grown, flux or flame fusion etc. naturals can also be flawless.
Synthetic sapphires also differ from natural sapphires in some mechanical behaviors. From what I understand, natural sapphire crystal nucleation and growth happens in a way that promotes isotropy, while the rapid nucleation and growth methods of synthetic sapphires promotes anisotropy.
One can see the cause of this very easily under a high power microscope, synthetic sapphires have parallel curved growth grains. At the inflection of point of the stria, the sapphire crystal layers are very prone to flaking and chipping due to shearing stresses (but not normal stresses). This happens especially in high end watches with sapphire crystals, the rim of the crystal (where it meets the bezel) will often be chipped. Natural sapphires lack these defined growth lines, and hence crack propagation via these grain boundaries will not happen as readily.
In other words, synthetic sapphires have weaknesses at certain points when impacted by force vectors in specific directions due to the manufacturing process being uniform and predictable.