This section is from the book "Bepler's Handy Manual of Knowledge And Useful Infomation", by David Bepler. Also available from Amazon: Bepler's Handy Manual of Knowledge and Useful Information.
French paste used in making artificial diamonds is a kind of glass with a mixture of oxide of lead. Imitation stones are now so nearly perfect that the market of real diamonds is beginning to suffer.
French chemists now reproduce the dichroism of the sapphire, and the composition of rubies of which the base is phosphate of lime.