or Lapis Lazuli, is a blue stone, generally intermixed with white veins and gold-coloured spots. Wallerius considers this stone as a species of jasper; and Cronstedt, more justly, as a species of that order of earths which have been lately called zeolites. Mr Margraaf, and also Mr Cronstedt, have made experiments on this stone, carefully cleansed from all white, pyritous, or heterogeneous matters. From these experiments we learn, 1. That this stone is soluble in acids without effervescence; and when it has been previously calcined, it forms gelatinous masses with acids. 2. That by calcination it is not deprived of its blue colour, till at least that operation has been long continued. 3. By a violent fire it is fusible, and forms a frothy glaas, sometimes whitish, and sometimes of a dusky yellow-colour, but always clouded with blue spots. 4. Fused with nitre, and thrown red-hot into water, it tinged the water with a blue colour, which disappeared in some hours. By this operation the stone lost its blue colour. 5. Some of this stone, powdered and mixed with glaas frit, produced a transparent citron-coloured glaas. With borax, it produced a glaas of a chrysolite-colour. 6. It gave no signs of its containing copper, notwithstanding it has been considered as an ore of copper by most authors. 7. It showed marks of iron, by forming a blue precipitate, like Prussian blue, when a phlogisticated alkali was added to a solution of this stone in acids. 8. Margraaf says, that by adding vitriolic acid to solutions of this stone in nitrous and marine acids, a white precipitate was formed, which he supposes was calcareous earth. Nevertheless, Mr Cronstedt affirms, that this stone does not effervesce with acids. Perhaps the calcareous earth was not essential, but only accidental. 9. Cronstedt says, that a precipitate is formed by adding a fixed alkali to a solution of this stone in vitriolic acid, which, being scorified with borax, yields a regulus of silver. He says, that by scorification with lead, two ounces of silver have been obtained from a hundred pounds of the stone. Mr Margraaf does not mention that he found any silver, or that he searched for any. Perhaps it is only accidental. The fine blue substance called ultramarine is prepared from lapis lazuli in the following manner, according to Wallerius. The stone, first finely levigated and mixed with linseed oil, is to be added to a paste, made by mixing together equal parts of yellow wax, colophony, and pitch, that is, half a pound of each, with half an ounce of linseed oil, two ounces of turpentine, and two ounces of mastic. To three or four parts of this paste one part of the levigated stone, mixed with linseed-oil, is to be added; and after the mixture has been digested together during three or four weeks, it is to be thrown into hot-water, and stirred till the blue colour separates and diffuses in the water, which is then to be poured off. The blue matter is allowed to settle; and, when dry, is the ultramarine required.

The lapis lazuli is found in many parts of the world; but that of Asia and Africa is much superior both in beauty and real value to the Bohemian and German kind, which is too often sold in its place.