Mr Haidmger on Polyhalite. 247 



I'he name of polyhalite was afterwards applied by Mr Ber- 

 thier to several substances found at Vic in Lorraine, and of 

 which he also published the following analyses : — 



Red massive. Red crystallized. Grey massiVe. 

 Sulphate of soda 44.6 21.6 29.4 



Sulphate of lime 45.0 52.2 40.0 



Sulphate of magnesia 0.0 2.5 17.6 



Muriate of soda 6.4 18.9 0.7 



Oxide of iron and clay 3.0 5.0 4.3 



The first of these, if we may infer anything from the mixture, 

 which is the only datum we have to proceed upon, appears to 

 be massive glauberite. The other two so much differ from 

 Stromeyers polyhalite in regard to chemical composition, par- 

 ticularly as one contains soda and the other potassa, that it 

 would have been better to have given them also a separate 

 name, when it was impossible to establish their identity, found- 

 ed upon an agreement in their physical properties. 



It is only from crystallized, or at least from such crystalline 

 varieties as are evidently homogeneous, that any thing like 

 exact information can be derived, both as respects the physical 

 properties, and the chemical constitution of a substance. I was 

 fortunate enough, during my late stay in Vienna, to obtain two 

 specimens of the polyhalite from Aussee for examination, whose 

 ^yery aspect and crystalline character precludes the possibiUty 

 of their being mere mechanical aggregates of different species 

 of salts. One of them was given me by Baron Leithner as a 

 new species of salt, containing potassa ; for the other I am in- 

 debted to Mr Von Pittoni, who had got it as the glauberite 

 from Aussee. 



A hexahedral form has been sometimes ascribed to the poly- 

 halite, said to be obtained by cleavage from certain colourless 

 masses mixed up with the fibrous mineral. Such, however, 

 when they occur will be found to be rock-salt, as in every in- 

 stance within my knowledge, or perhaps anhydrite, whereas 

 the actual forms of polyhalite belong to the prismatic system of 

 Mohs, and are broad six-sided prisms, similar to Plate I II. Fig. 4. 

 The angle produced by two adjacent faces o is about 115°, the 



