22 DESCRIPTIONS OF MINERALS. 
Sylvite.—Potassium Chloride. 
Isometric. White or color'ess, with vitreous lustre, and 
taste nearly that of common salt. ‘he crystals are ‘often 
cubes with octahedral planes, like fig. 8 on p. 19. H.=2. 
C= i-9-2: | 
Composition. K Cl=Chlerine 47-5, potassium 52°5 =100. 
From Vesuvius, about the fumar oles of the voleano. 
Halite.—Common Salt. Sodium Chloride. 
Isometric. In cubes and other related forms. Some- 
times crystals have the shape of a shallow four-sided eup, 
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, some ares Bene. yel- 
low, and of amethystine tints. ‘l'aste saline. H.=2. ce 
2207. 
Composition. NaCl=Chlorine 60-7, sodium 39:3=100. 
Crackles or decrepitates when heated ; fuses easily, coloring 
the flame deep yellow. 
Diff. 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 W ielicaka ; at Hall in the Tyrol, and along a 
range through Reichenthal in Bav aria, Hallein in Saltzburg, 
Hallstadt, Ischl and Ebensce in Upper Austria, and Aussee 
in Styria; in Hungary at Marmoros and elsewhere ; in 
Transylvania, Wallachia, Galicia and Upper Silesia; at 
Vie and Dienze 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 Hungar y. The former, near Cracow, have been worked 
since the ° year 1251, and it is caleulated that there is still 
