336 EXPERIMENTS RELATIVE TO METEORITES. 



transformation of peridotic rocks; there are tliose^in effect, wliicli have been con- 

 sidered as being derived from pyroxenicand other rocks. It is proper to observe 

 on this occasion that the experiment by whicli I have shown abcjve with what 

 facihty peridot is transformed inro sihcates less basic well explains, in general, 

 the numerous transitions of serpentine to other rocks, as, in the first place, to 

 euphotide, which is so ordinarily associated with it, as well as to the dioritesand 

 pj-roxenic rocks, the prasophyres, &c., which accompany it in Tuscany,* in dif- 

 ferent regions of the Alps and in many other countries. 



The analogies which subsist between serpentine and peridotic rocks have led 

 to an examination of the former in reference to the synthesis of meteorites. If 

 we melt serpentine in a brasque of charcoal the grains of iron which are sepa- 

 rated from it often include nickel in considerable proportion, as when we operate 

 upon peridot. For example, the iron extracted from the serpentine of Sainte- 

 Sabine, in the Vosges, contains 0.67 per 100 of nickel. That of a serpentine 

 of Mount Genevre has yielded it also, but. in quantities too minute for accurate 

 apportionment. t 



To these traits of similarity of composition between serpentines and meteorites 

 is to be added the presence of chrome. On the one hand, chrome is found in 

 most of the serpentines, not only in the state of a green comliination, | l)ut also 

 in the state of cln-omated iron, as is observed in the most different coinitrics. § 

 On the other hand, the important observation made by Laiigierin 1806, \\ namely, 

 that chrome is rarely absent in meteorites, has but acquired confirmation. There 

 are, in effect, very few stone-meteorites which are not mixed, at least in a small 

 proportion, with chroniite or chromated iron. Thus, apart from its persistency 

 in water, serpentine maybe assimilated to meteorites of theconmion type, almost 

 as rightfully as peridot and Iherzolite. It is proper further to remark that the 

 carbonaceous meteorites (Cape of Good-Hope, Kaba, and Orgueil) appear to con- 

 tain a hydrated magnesium silicate, which M. Wohler states to be analogous to 

 serpentine. 



I will add an observation on the formation of spinelle, ■which Is sometimes dis- 

 seminated in peridot, as is seen in some localities of the Haute-Loire, in the Iher- 

 zolite of the Pyrenees, and in the serpentine Iherzolite of Baldissero. 



Peridot being the most basic rnagnesian silicate which the rocks afford, the 

 presence of this spinelle seems susceptible of easy explanation. As the alumina 

 was disseminated in a very basic silicate, with which it could not dispute the 

 silicium, nothing remained for it but to unite with the bases, magnesium and 

 protoxide of iron. I have confirmed this supposition b}' a synthetic experiment. 

 If we fuse the natural peridot, at a very high tenqjerature, with alunnna, (10 per 

 100,) we shall see, after the fusion, in the crystaUine peridotic mass, small black 

 grains which are infusible, unaltered by acids, and which contain, at once, alu- 

 mina, magnesium, and protoxide of iron ; some of them exhibit the form of the 

 regular octahedron. Tliese crystals, all of which have the characters of pleo- 

 naste spinelle, furnish a perfectly satisfactory reason lor the formation of this 

 mineral in the peridotic and the Iherzolithic rocks. 



CHARACTERS WHICH DISTINGUISH PERIDOTIC ROCKS. 



Among the characters of peridotic rocks there are three which clearly distin- 



* Paul Savi, Delle liocce qfioiitiche delta Toscana, 1838, p. 11. 



+ It is proper to recall ou this occasion that the uickel lirst indicated by Stromeyer, in cer- 

 tain serpentines, at the same time as in peridot, has since then been found in the serpentines 

 of regions far remote from one another — in Saxony, in Silesia, in Norway, in Texas, in Penn- 

 Bylvania ; this metal is not wanting in the serpentines of Canada, according to the analyses 

 of M. Sterry Hunt, {Geology of Canada, p 471.) 



t Indicated long since by Valentine Rose and Klaproth. 



$ Department ot the Var, Saxony, Baden, the Austrian Alps, Moravia, Scotland, Norway, 

 Greece, the Ural, numerous depositories in the United Sta'.es, Canada, &-c. 



U Annales du Museum, t. vii, p. 393, 18UG. 



