THE HALOID COMPOUNDS 329 



B.B. Fuses at two (790) and colors the flame violet (K). If 

 much sodium is present, the blue glass should be used. With 

 S. Ph. bead saturated with copper oxide yields an azure blue flame 

 (Cl). Dissolves easily in water, yielding a saline taste. 



General Description. Crystals are usually small cubes and less 

 oft fii in combination /with the octahedron; other forms are rare. 

 The variation in color of specimens is due to impurities, as in the 



FIG. 407. Sylvite from Stassfurt, Prussia. 



case of halite, as pure potassium chloride is white. Its holoaxial 

 symmetry is clearly shown by the asymmetrical position of the 

 square etch figures in relation to the edges and diagonals of the 

 cube faces. 



Sylvite is more soluble than halite, and is therefore deposited at a 

 later stage in the concentration of complex salt solutions, or, in the 

 sequence of the deposit, sylvite will lie above the stratum of halite 

 and will be mixed with the more soluble magnesium compounds, 

 from which at times sylvite may be formed as a secondary mineral. 



All rock salt contains potassium chloride in small amounts, but 

 the most noted deposit of potassium salts is that of Stassfurt in 

 Prussia; smaller deposits of the same general nature are also 

 found in Austria. It is from these European localities that the 



