Lapis Lazuli Enlarge
Aug 1 1811 published by Jas Sowerby London.
Exotic Mineralogy
XV
Silex Lazulum

Lapis Lazuli

  • Syn.
    • Lazulite. Haüy 3. 145. Tabl. comp. 47.
    • Zeolithe bleue ou Lapis Lazuli, pierre d’azur. De Born 1. 201.
    • Lazur-stein. Emmerl. 1. 212.
    • Lapis Lazuli. Kirwan 1. 283.
    • Azurite. Sowerby’s Catalogue, p. 1. 58.

This substance has been long conspicuous for the astonishing brilliancy and permanency of the colour which it produces, and when prepared for use is commonly called Ultramarine, of which there are such numerous examples in the illuminated missals, often of such exquisite labour, and so highly preserved by the choice and lasting colours used in them, as to stamp them almost invaluable.

It is found chiefly in Persia, also in Great Tartary, Siberia, China, and America, and has been much employed by the Chinese and others in painting China; when reduced to powder for the above use, it is sold, according to the pains taken to select the most pure and brilliant, from five to fifteen guineas, or more, per ounce.

The stone is more or less pure in moderate masses, but is seldom without some Sulphuret of Iron (Pyrites) in specks or veins and often particles of Mica: the separating it from the former requires some dexterity. This substance scratches glass; has but little transparency, is coarse grained, splintery, and rather brittle. It is said to have been found crystallized in garnet dodecaëdrons. Before the blow-pipe it melts into a white enamel: calcined and reduced to powder, it becomes like a jelly, by the action of acids. Spec. Grav. according to different Authors 2.771 to 2.896.

Analysis by Klaproth
Silica 46.    
Alumina 14.50
Carbonate of Lime 28.    
Sulphate of Lime 6.50
Oxide of Iron 3.    
Water 2.    
100.0

The Lapis Lazuli was formerly cut and polished for rich inlaying and Mosaic work; it has been used for etuiee-cases, and is now used for snuff-boxes and ornamental jewellery. The mixed nature of the specimens render analysis uncertain, wherefore this substance has by some been considcred the same as the Azurite, and the similarity of names causes confusion.

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