NEW PITCHLIKE IRON OTIE. 



S55 



these lead ores, at the depth of 494 feet [527 Eng.], that this 

 resiniform substance was found. It appeared to have been 

 Bffi^ted over several pieces, which were impregnated with it; 

 and was commonly in very brittle, drusy masses. 



I have only a few fragments of this left, and they exhibit The two com- 

 nearly the same characters as Ferber's pifchlike iron ore, ^'^'^'^* 

 which may now be termed sulphated iron with excess of 

 base. Dr. Weiss, of Leipsic, who was present at some ex- 

 periments I lately made with the two substances, did not 

 hesitate to consider them as tlie same. In fact, the sub- Their chaiac- 

 stance of Huelgoat and that of Freyberg have both a deep ^'^'*" 

 yellow colour, varying between that of olivine and idio- 

 crase : their aspect is equally resinous; their fractjire is 

 conchoidal, unequal, shining; their hardness superior to 

 that of sulphate of lime, but inferior to that of carbonare 

 of lime, which scratches them strongly, though they also 

 scratch it slightly; their brittleness is very great; their 

 colour, when scraped, is yellow, though that of the Freyberg 

 mineral is a little deeper than the other. 



In the flame of a candle, before the blowpipe, they swell 

 ^up, and crack, assuming the colour of gamboge in the 

 lump; and at length melt into black scorias, attractable by 

 the magnet, which adhere to the platina tongs. The mine- 

 ral from Freyberg only swells up more, melts more quickly, 

 and adheres more to the tongs. 



When fresh, the resiniform mineral of Huelgoat gave aEvidenre'of 

 white precipitate with the solution of barytcs in muriatic ^"'i''^"'^'-' ^'^'''" 

 acid, which indicated the presence of sulphuric acid; and 

 it impressed then an acid and styptic taste on the tongue, 

 which it has now lost: but the presence of sulphuric acid 

 in it has been confirmed afresh by Mr. Descotils, though he 

 had not enough to verify that of phosphoric acid. 



cent of phosphorus, by a simple, new, and speedy method, de- 

 . scribed in that paper. I was led to it by the green flame, which I 

 observed to rise from the crucibles in which I heated the ore. In 

 the same way I was induced to suspect tlie presence of phosphorus 

 in the resiniform ore accompanying this lead from tlie green flame 

 I obtained with the blowpipe, and the white precipitate it gave 

 •with lime-water. See Journ. de Phys,, May, 1786, vol. xxviii, 

 p. 382, 385, 



A a 2 V. Analysis 



