58 



PEOE. T. G. BONNET ON THE 



[Feb. 1903, 



This on examination proved to be an indubitable serpentine, dark 



in colour and apt, 



Pig. 3. — The Fi.lon Licone. 





owing to the effects 



of pressure, to break 



__ up into small pieces. 



[Rough diagram showing the relation of the 

 magnetite and serpentine.] 



1 — Calc-mica-scliist ; 2= Magnetite; 3 = Serpentine 

 (the positions of specimens described in the 

 paper are indicated thus, +) ; -± = Slope of debris 

 and turf: this is greaty contracted, the diagram 

 being intended only to show the unquestionable 

 relation of 2 and 3. 



The Eilon Larsine 

 is a considerable 

 height up the steep 

 left bank of the 

 Vallon de Grauson : 

 its association with 

 a mass of serpentine 

 is equally clear, and 

 this, which here 

 plunges steeply down 

 towards the torrent, 

 has calc-mica-schists 

 on both sides, the 

 lower mass locally becoming an almost pure marble. 3 The ser- 

 pentine appeared to me to be a continuation of the one already 

 named ; and I find that Cavaliere Jervis says : 



' Essa e aperta sopra il prolungamento del giacimento di Licony (sic), per cui 

 la sua natura geologica e identica.' 2 



The openings here are at more than one level on the hillside, but 

 we were satisfied with visiting two or three. The magnetite 

 seemed to be as pure as at the Licone mine, but to occur in smaller 

 masses, for the galleries were not so large, and the mixed rock could 

 be found cropping out within a very short distance, in one case 

 actually at the side of the gallery, followed in a few yards by a 

 serpentine, which appeared fairly normal. 3 Here the relation of 

 the magnetite and serpentine was more easily studied, and we had 

 no doubt that the one graduated into the other. 4 



Examination with the microscope confirms the field-evidence. It 

 seemed useless to slice my specimens of the ore, for these appeared on 

 examination with a strong lens to be practically pure magnetite, and 

 the specific gravity of one, determined by a Walker's balance, is 

 4*6J: 5 ; but I have studied specimens of the serpentine and the 



1 A crag of this had apparently fallen and destroyed the old path. 



2 ' I Tesori sotterranei dell' Italia' pt. i (1873) p. 93. 



3 There was plenty of serpentine and mixed rock in the spoil-bank of the 

 hillside. 



4 It may be worth mention that there are two outcrops of serpentine close to 

 the torrent in the Vallon de Grauson, which are probably a continuation of the 

 same mass, and the higher one seems very ferruginous. The calc-mica-schists 

 are also visible, and lower down the valley, near some chalets named Monro, is 

 an outcrop of quartz-schist, very like that which I have seen associated with 

 the former rock in many other parts of the Alps. 



5 It is a difficult specimen to work with, and I am not quite satisfied with 

 this result. A small chip (not from it) weighed by Mr. Elsden, of University 

 College, London, at the kind request of Prof. Sir William Ramsay, gave sp. gr. 

 = I # 6088. This specimen, however, contained a few steatitic spots. 



