What is the problem with crystals in Sapphire and Ruby?

[pyramid]

In a previous post Garry Holloway (Cut Nut) mentioned the problem with crystals in Sapphire and Ruby? What is the problem? I now that sapphires are heated for colour improvement.

 

[pyramid]

I take it the problem is with heat treating sapphires and rubies as I have found in this article.

This should be in the colored stones section I now realise however it also states that jewellers can have problems with natural unheated sapphires as when repairs are being carried out on jewellery a crystal may expand and cause damage since it has never been heated before. It states that the heat treated sapphires which explode during the heat treat process to improve color would be recut or discarded at the time of the process.

Mmm, maybe we should buy heat treated after all. I don't know though about high quality sapphires maybe they are chosen with no crystals in them to begin with.


http://www.ganoksin.com/borisat/nenam/ajm-corundum.htm

 

[Garry H (Cut Nut)]

If you heat a diamond with a crystal nothing bad happens like it would with most corundum's with xstals.

Re read the previous thread Pyramid