298 DESCRIPTION OF THE MUSEUM. 



moonstone , or mother of pearl felspar, the ground 

 of which is of a sky-blue ; the avanturim, of a 

 carnation or green colour, spotted with gold 

 coloured and white dots ; and lastly, the ama- 

 zon stone, or green felspar, the surface of which 

 in certain lights looks like satin. There is a beau- 

 tiful specimen of this variety on the first shelf, 

 above the stage for study. The kaolin, or de- 

 composed felspar, is of a great use in making 

 porcelain. 



Several varieties of tourmaline, in the twenty- 

 seventh case, are employed by jewellers ; but it 

 is chiefly remarkable for its electrical properties, 

 when heated. Beyond the stage is a superb spe- 

 cimen of the red acicular variety, called siberite. 



The amphibole and pyroxene, whose numerous 

 modifications fill this case, are chiefly interesting 

 to mineralogists for the important share they have 

 in the structure of the terrestrial globe. On one 

 of the upper shelves is a beautiful group of py- 

 roxene crystals of the quadrioctonal variety, given 

 by M. Muthuon, engineer of the mines of France. 

 Below, in the twenty-eighth case, is a magnificent 

 specimen of silky amphibole from St. Gothard. 



The lazulite, which we see in the twenty-ninth 

 case, is better known under the name of lapis- 

 lazuli, or simply, lapis. That which is of a purple 

 blue is most sought for by artists, who work it into 



