KINDS OF ROCKS. 449 



n. SAUSSURITE-BEARING. 



6. Euphotide. (Gabbro in part.) — A grayish- white to gray- 

 ish-green, and sometimes olive-green rock, very tough, having 

 G. =2*9-3 *4. Consists of saussnrite of whitish to greenish 

 and bluish color, mixed either with smaragdite of emerald- 

 green color, or with green to grayish-green diallage ; the 

 diallage generally containing more or less hornblende, and 

 the smaragdite, pyroxene. The saussurite is commonly of 

 either the first or second kind mentioned on page 410 ; but 

 the distribution of these kinds is not fully made out. Labra- 

 dorite is rarely present locally in place of the saussurite. 

 Metamorphic. 



Varieties. — a. Diallagic ; diallage the chief foliated mineral, b. 

 Smaragditic ; emerald-green smaragdite, the foliated mineral, e. Mi- 

 caceous; contains mica. d. Serpentinous ; contains some serpentine — 

 a rock into which it often graduates, e. Garnetiferous. f . Schistose ; 

 especially so when talc is present, g. Variolitic ; contains aphani- 

 tic concretionary spheroids of the saussurite mineral, as in the ' ' Vario- 

 lite de la Durance," and of Mt. Genevre, and asociated with ordinary 

 euphotide ; for which concretions Delesse obtained the composition 

 Silica 56 12, alumina 17*40, chromium oxide 0*51, iron protoxide 7*79, 

 magnesia 341, lime 8*74, soda 3*72, potash 0*24, ignition 1 -93=99*86, 

 and the specific gravity 2*923. The variety obtained at Orozza is the 

 Verde di Corsica, of decorative art. 



Occurs near Lake Geneva, in Savoy ; at Mt. Genevre in Dauphiny, 

 near the boundary between France and Italy ; at Allevard, in the 

 northeastern part of Isere ; in the valley of the Saas, north of east of 

 the Monte Kosa region ; in the Grisons ; near Leghorn and Bologna ; 

 near Florence, at Mt. Impruneta, it being the Granitone (page 450) 

 of the Serpentine region ; on Corsica, in the Orezza valley; in Silesia ; 

 in I. of Unst. It is often associated with serpentine ; and the serpen- 

 tine and euphotide form beds in irregular masses among, and as a 

 constituent part of, a series of metamorphic strata, which include 

 green chloritic and talcose schists, limestone (which, at Mt. Genevre, 

 is of the Jurassic formation \ and other rocks. For the Mt. Genevre 

 euphotide, Delesse obtained Silica 45 00, alumina and iron oxide 

 26*83, lime 8*49, magnesia, soda and potash (by loss) 13*90, water 

 and carbonic acid 6*78, and for the saussurite the result stated on 

 page 410. The composition is near that of a labradioryte, and the dif- 

 ference in the two rocks must have depended on the different condi- 

 tions attending crystallization. The mixture of hornblende and py- 

 roxene in either foliated constituent, in connection with their mutual 

 positions and structure, proves that part of the hornblende is altered 

 pyroxene. Ihe remark made on page 410 with reference to the pro- 

 duction of the saussurite may apply also to the foliated hornblende, 

 and therefore to the whole rock. 



