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. CXXXVII. Of Iargons of Avernia, and the Way to make those Red which are of a Gridelin-Colour.

WE have promised to treat of the Jargons of Auvergne, which are little Stones commonly found in that Country, and several other places of France: They are red and shining like Iacynth; which has gain'd them the Name of false Iacynths, because they much imitate that Precious Stone.

There are found, notwithstanding, many of these small Stones, which are not of a red Colour, but of a kind of Gridelin. You may give these last a Red Tincture, with as much ease as you can take it away from the former to convert them into Diamonds, as we will shew in the following Chapter.

To give a Red Colour to Jargons that are of a Gridelin, you must take equal parts of purified Sal-Armoniac, and of Tartar calcined to Whiteness, as we have otherwise shewn: Mix these Matters well in

fine Powder, then stratifie your Jargons in a Cruci∣ble S. S. S. beginning and ending with the Powders. Then put the Crucible in a good Coal-Fire, but not hot enough for the Stones to melt, but only to grow red hot, that they may be the better penetrated by the Tincture the Materials will give it, then let it cool, and by this Method they'll take as fine and shi∣ning a Red Tincture, as the true and finest Natural Jargons of this colour have.