224 DESCRIPTIONS OF MINERALS. 



Sylvite. — Potassium Chloride. 



Isometric. White or colorless, with vitreous lustre, and 

 taste nearly that of common salt. The crystals are often 

 cubes with octahedral planes, like fig. 8 on p. 19. H. — 2. 

 G. = 1-9-2. 



Composition. KCl=Chlcrine 47-5, potassium 52*5 =100. 

 From Vesuvius, about the fumaroles of the volcano. 



Halite. — Common Salt. Sodium Chloride. 



Isometric. In cubes and other related forms. Some- 

 times crystals have the shape of a shallow four-sided cup, 

 and are called hopper-shaped crystals ; they were formed 

 floating, the cup receiving its enlargement at the margin, 

 this being the part which, lay at the surface of the brine 

 where evaporation was going on. Cleavage cubic, perfect. 



Color usually white or grayish, sometimes rose-red, yel- 

 low, and of amethystine tints. Taste saline. H. =2. G.= 

 2-257. 



Composition. Na CI = Chlorine 60*7, sodium 39-3 = 100. 

 Crackles or decrepitates when heated ; fuses easily, coloring 

 the flame deep } T ellow. 



Biff. Distinguished by its taste, solubility, and blowpipe 

 characters. 



Obs. Salt occurs in extensive but irregular beds, usually 

 associated with gypsum, anhydrite, and clays or sandstone. 

 It occurs in formations of all ages, from the Silurian to the 

 present time. It exists in the Pyrenees, in the valley of 

 Cardona and elsewhere, forming hills 300 to 400 feet high ; 

 in Poland and Wieliczka ; at Hall in the Tyrol, and along a 

 range through Reichenthal in Bavaria, Hallein in Saltzburg, 

 Hallstadt, Ischl and Ebensee in Upper Austria, and Aussee 

 in Styria ; in Hungary at Marmoros and elsewhere ; in 

 Transylvania, Wallachia, Galicia and Upper Silesia ; at 

 Vic and Dieuze in France ; at Bex in Switzerland ; in 

 Cheshire, England ; in Northern Africa in vast quantities 

 forming hills and extended plains ; in Northern Persia at 

 Tiflis ; in India in the province of Lahore, and in the valley 

 of Cashmere ; in China and Asiatic Russia ; in South Amer- 

 ica, in Peru and the Cordilleras of New Granada. 



Among the most remarkable deposits are those of Poland 

 and Hungary. The former, near Cracow, have been worked 

 since the year 1251, and it is calculated that there is still 



