One of the greatest gemological challenges is determining if a ruby or sapphire has been heat treated. UV fluorescence can assist in that identification, as well as detecting fillers in emerald.
For those who wish to explore the literature of inclusions in gemstones further, we have selected the following articles and books that are of particular merit. Most of these are cited in the Lotus Gemology Hyperion Inclusion Database, but are listed below in a more convenient summary format. Many of the links will allow you to download a PDF copy of the original article.
A loving look at ruby from the standpoint of the connoisseur.