476 Hie American Naturalist. [June, 



in a partially crystallized lava. It was evidently the last component 

 to solidify. The composition of the rock is as follows : 

 Si0 2 A1 2 3 Fe 2 0, FeO CaO MgO Na a O K 2 H,0 P 2 5 Total 

 47.85 13.24 2.74 2.65 14.36 5.68 3.72 5.25 2.74 2.42 = 100.65 

 This composition is so similar to that of the Ycsuviun lcucitophyres, 

 that the rock is regarded as the plutonic equivalent of these lavas. 

 The low percentage of silica and the high lime percentage separate the 

 rock from the eleolite syenites. 



One form of the nepheline-malignite is panidiomorphic through the 

 development of the orthoclase and all the other components in crystals. 

 In the garnet-pyroxene phase of the rock the orthoclose is intergrown 

 with alhite in the form of phenocrsyts imbedded in a hypidiomorphic 

 aggregate of aegerine-augite, melanite, biotite, titanite and apatite. 

 The augite, melanite and biotite are allotriomorphic. They seem to 

 have crystallized contemporaneously with each other, and with a part 

 of the orthoclase. In the amphibole-malignitethe distinguishing char- 

 acteristic is the prevalence of a very strongly pleochroic amphibole, 

 and the absence of any large quantity of aegerine. The augite that is 

 present occurs intergrown with the amphibole. Melanite is wanting, 

 otherwise this rock is very much like the mellanite-pyroxene raalig- 

 nite. 



The author points out the fact that the great mineralogical differ- 

 ences observed in the three types of malignite, are accompanied by 

 very slight differences in chemical composition. The three types are 

 regarded as differentiation phases of the same rock mass. 



Foliated Gabbros from the Alps.— Schafer* gives an account 

 of the olivine gabbro and it- dynamically metamorphosed forms which 

 constitute the rocks of the region in the vicinity of the Allalm glacier 

 between the Zermatthal and the Saarthal in the Alps. The normal 

 gabbro contains in its freshest forms much or little olivine. In its 

 altered forms it consists of saussurite, amphibole, talc, actinolite and 

 garnet. Ottrelite is often found enclosed in the talc and sometimes im- 

 bedded in the saussurite. In one of the granular varieties of the met- 

 amorphosed gabbro a blue amphibole is very abundant. It is inter- 

 grown in part with omphacite. The granular alteration forms of the 

 gabbro pass gradually into foliated forms and through these into rocks 

 called by the author " green schists." The schistose gabbros are min- 

 eralogically similar to the granular alteration phases of the rock, 

 except that they contain in addition to the minerals named above a 



3 Neues Jahrb. f. Min., etc.. B.B., p. 91. 



