The art of glass shewing how to make all sorts of glass, crystal and enamel : likewise the making of pearls, precious stones, china and looking-glasses : to which is added, the method of painting on glass and enameling : also how to extract the colours from minerals, metals, herbs and flowers ... : illustrated with proper sculptures / written originally in French, by Mr. H. Blancourt, and now first translated into English ; with an appendix, containing exact instructions for making glass-eyes of all colours.

CHAP. CXXXIX. The Way to make Diamonds.

THE Quality and Colour of the Diamond being so well known, we shall not enlarge upon them in this Chapter, but only shew the way to counter∣feit them, make them endure the Fire, and harden them.

Take of good Natural Crystal, calcined and redu∣ced to subtile Powder, what Quantity you please; fill a Pot with it, and set it in a Glass-house Fur∣nace twelve Hours to be melted and purified: Then drop the melted Matter into cold Water, then dry it, and reduce it again to Powder; add to that Pow∣der its weight of our fine Salt of Tartar, of Chap. 93. Mix these two Powders well, and make little Pills of them with common Water. Then wipe these Pills, and put them into an Earthen Pot on a strong Fire, there to grow red hot for twelve Hours space without melting. Then put them into a Pot in a Glass-house Furnace, where leave them two Days, to be well melted and purified, then put the Matter twelve Hours in the An∣nealing Furnace to cool little by little. Then break the Crucible, and you'll have a fine Mate∣rial for Diamonds, which cut and polish at the Wheel.