gems, jade, Fischer-Book, glyptic arts, glyptic

Sinkankas: This interesting and worthy text is divided into two distinct and actually unrelated parts, the first being a course of instruction for apprentice jewelers and the second descriptions of large and famous gems. Each part is paged separately, the first written as a dialogue between a certain Litofilo, who asks the questions, and the expert, Didattucolo, who answers them. During the dialogue much is elucidated on the reasons why gems are held in high esteem, with examples of diamond prices (taken from Tavernier, De Boodt, Mosquera, Dutens, etc.), together with comments on the principal gem-producing regions, weight systems for gems, commerce in rough and cut gemstones, forms of rough, cutting, hardness, and the absence of flaws as vital to final value. Following sections describe the gemstones, beginning with a large treatise on diamond, then passing on to ruby, spinel, opal, sapphire, topaz, zircon, emerald, and others, including the crystalline and chalcedonic varieties of quartz, jades, petrified wood, various ornamental materials, stones useful for engraved gems, lapis lazuli, aventurine, coral, and pearl, the latter treated in considerable detail and subdivided according to types and shapes. All of it is non-technical, though references are made in places to the formal mineralogies of Wallerius, Romé de l’Isle, and others. The second part of the book describes 26 large or famous gems, each illustrated by an engraving in which shading is imparted as well as the usual sharp lines of the burin. Most of the illustrations are copied from Tavernier and include the Grand Mogol and Grand Duke of Tuscany diamonds, among others, together with several examples of large pearls. All gems are identified in the text, their weights given, and shown at natural size in the engravings. A rare work.