I've definitely heard of lead glass filled rubies, a much more common practice nowadays. Sapphires, unsure if that is the case with those though.I noticed this was Effy - I remember there was a lot of controversy a while back, about them using sub par stones...but I believe it was in association with Macy's switching out stones.
http://sfpublicpress.org/news/2010-07/macys-sells-rubies-filled-with-glass