>s A SYSTEM OF 



form. At Schneckenftein in Saxony, thefe 

 criftals are found of a prifmatical ocl:- 

 oedral form, with no points, but flat, 

 and with ibrne facets at the top •, however 

 without doubt the oriental topazes have ano- 

 ther figure *. 



Experiments by fire have been made on 

 the Schneckenftein topazes by Mr. Pott^ 

 as may be feen in his Lithogeognefia. 



To this kind I refer 

 a. The pale yellow topaz. 



Which is nearly uncoloured, and is found 



at Schneckenftein. 

 h. The yellow topaze, from Schneckenftein. 

 r. Deep yellow, or gold coloured topaz, or 



Oriental topaz. 

 d. Orange coloured topaz. 



SECT. XLVL 



JE. The yellowifh green topaz, or Cbrffolite. 

 Is of a grafs green colour, and maf 

 perhaps belong to fome other fpecies, which 

 might be difcovered, if it could be ob- 

 tained rough, or in its matrix, and large 



* I have got fome rough Brazil topaxes, which are prifma- 

 tical, and of a rhomboidal quadrangular figure, pointed at 

 one end ; btlt as thefe feem to be broke off at the other 

 end, it is very likely, that they, as well as many other 

 criftals, may be pointed at both ends, when nothing has 

 impeded them during their criftallifation. 



Befides thefe, I have got fome fragments of other topazes, 

 Hkewife faid to be from the Brazils, which are all of them 

 prifmatical, but plainly fhew, that fome are pentagonal, and 

 other regular hexagons with points. 



The topazes lofe their colour in the fire, but fome of them 

 turn red in a certain degree of heat, and are therefore very 

 much ufed initcad of the pale rubies, and even are often fold 

 as fucli. 



enough 



