I just went to a jeweller to try to get a loose blue diamond set into a new mounting. I was told they don''t take any loose stones that have never been set before in case they are synthetic and "blow up". She said they had a lady bring in a ruby that was appraised three times as being genuine only to have it "blow up" under the heat of the torch because it was some kind of extremely good ''paste'' stone. I couldn''t beleive my ears! I have a faux alexandrite I want to set so am now worried about it. And I bought what was listed as a heated pad saphhire (but could be a synthetic??) and am now worried about it, too. Is this true or just paranoia?