114 Professor T. G. Bonney — 



specimen makes it fairly certain that the noumeite is in a crypto- 

 crystalline condition, like chalcedony, steatite, etc.^ Both Dana and 

 La Croix quote a nnniber of analyses, which show that noumeite 

 must be a very variable silicate.* Professor Liversid^e states that 

 these nickel silicates occur as veins in or incrustations on a brownish 

 or plum-coloured serpentine. There is, therefore, a considerable 

 probability that a nickel mineral of the genthite group may enter 

 into the composition of some of these Alpine serpentines. Generally, 

 no doubt, the amount is small, but I have occasionally noticed 

 a rather peculiar mottling of a rich apple-green material (which 

 now reminds me of the noumeite) and of a purplish one in the 

 Alpine serpentines (recalling the plum-coloured tint just mentioned). 

 Without forming any very definite opinion, I had been disposed to 

 attribute this apjjearance to pressure, but it now occurs to me that 

 it may be due to the presence of hydrous nickel silicates. 



It is well known that serpentine is by no means rare in the Alps. 

 The rock is usuall}^ associated with the above-named group of schists, 

 but occurs, though rarely, in the gneisses. Its most common associate 

 is the green-schist. As I have already stated, there are two principal 

 varieties, one containing bastite, the other augite (though sometimes 

 both minerals are present), and the rock is always, or almost always, 

 a dark green in colour. Sometimes the serpentine seems normal in 

 character, but it is often more or less affected hy pressure, passing 

 from a stage where it breaks into irregular or lenticular " slicken- 

 sided " flakes, to that where it is fissile, like a slate. Occasionally 

 we can find distinct evidence that it is an intrusive rock ; more often 

 this has to be inferred from the way in which the masses occur, and 

 their outline on a map. The outcrops in the Zinal district are few 

 and small, the largest known to me being on a lofty ridge called the 

 Crete de Million.^ Here it is clearlj' intrusive in the green-schist, 

 a mass of which it includes, together with another of a whitish 

 quartzose rock. Some of this serpentine exhibits the effects of 

 pressure, but parts of it have escaped very well. It is the augitic 

 variety. I have examined specimens representing the two extremes 

 of structure. As they differ little from other Alpine serpentines of 

 which accounts have been published,* it is needless to enter into 

 minute descriptive details, and I will notice them only so far as they 

 throw light on the " topfstein." 



^ See also La Croix, " Mineralogie de la France et ses Colonies," vol. i, p. 438. 

 He speaks of noumeite as either crypto -crystalline or amorphous. 



* To speak only of the nickel-oxide, that varies "generally from 22'0 to just over 

 45'0 ; but in one case 14*6, in another 10'2, and in a third only 2-32. C. A. Miinster, 

 quoted in Min. Mag., vol. x, p. S9, says that he has found nickel-oxide replacing 

 magnesia in olivine, serpentine, steatite, etc. Professor Liversidge suggests that the 

 formula of noumeite may be 2 Mg 3 Si O3 2 H^ 0, where some of the magnesium 

 is replaced by nickel. 



^ I am indebted for notes and specimens of this mass to my friend, Mr. J. Eccles, 

 F.G.S., but I had a remarkably good view of it at a distance of about half a mile, 

 during the ascent of a neighbouring peak. As I know him to be one of the most 

 accurate of observers, and the glen leading to the base of the Crete is very stony 

 and uninteresting, I absolved myself from undertaking a tiresome walk. 



* By various authors, myself included. 



