The tungfleln is alraoft always mechanically mixecl with Defcripdon of 

 Llack amphibole (hornblende), ftriated adinote, of a clear '^"^°'^^* 

 green colour (JhnrlJ, mica, fulphurated copper^ bifriiulh, and 

 fulphurated molybdena> which may be eafily known by ex- 

 pofing it to the fire. 



The cerite, properly fo called, is tranfparent, of a flefli Phyfical proper^ 

 colour, fometimes deep and fometimes bright, feldom yellow-^^" °^""^'^* 

 ifli. In a mafs, or in fmall fpecimens, the (lone is of an ir- 

 regular form ; its fra6lure is indeterminate, compafl, and a 

 little brilliant, with obtufe edges; its conliftence is tenacious 

 and flrong; it gives fire with fteel with difficulty, but does 

 not fcratch glafs ; it is not attra6led by the magnet ; after 

 having been made red-hot in the fire, it lofes its bardnefs, 

 and fix or feven per cent, of its weight : by this operation it 

 becomes friable, and acquires a bright yellow colour : it does 

 not melt alone. 



On account of its weight, Cronftedt has placed it among Is the falfe tung- 

 the tungfteins, in his Mineralogy. In pure fragments, it is ^^^^^ °^ S*^^^^^^« 

 to that of water as 4.733 and 4.935 to 1.000. Scheele not 

 having found wolfram in it, called it falfe tungftein. 



The conftituent principles of this mineral were given by Conflituent 

 Bergman, in the Memoirs of the Academy for the year 1784,''''^'"'^^^^'' 

 page 121, from an analyfis of D'Elhuyar: they are as fol- 

 lows : — 



Silex, - - - 0.22 

 Iron, - - - 0.24 



Lime, » * - 0.54 



1.00 



Heated with borax by the blow-pipe, it forms a globule of Mabltude with 

 glafs, which, while hot, appears greenifh, but is colourlefs ^'*'^^'^* 

 when cold. Urged with carbonate of foda in a platina fpoon 

 it is not diflTolved. 



§ n. 



Analyfis of the Proportions of Cerium^ 



TO fcparate the yttria which was fuppofed to be in it, it Treatment o^ 

 was reduced to a fine powder in a porphyry mortar ; pure . "^"^^j^'? *^** 

 concentrated nitric acid was then poured upon if. The acid 

 was decompofed, and a coniiderable quantity of nitrous gas 



! U2 and 



