312 Spurr — Scapolite Hocks from Alaska. 



which is colored brown with iron oxide. There are abundant 

 microscopic inclusions arranged in zones within the crystal. 

 Judging from the paucity of calcite among the decomposition 

 products and also from the apparent small single and double 

 refraction of these scapolites, the mineral is probably a soda 

 scapolite (marialite end of the series). By exception, some 

 almost entirely altered phenocrysts now consist chiefly of cal- 

 cite, but what remains seems to be scapolite, and the outlines 

 of the phenocrysts corroborate this inference. These decom- 

 posed scapolites are probably lime scapolites, or meionites. A 

 few small phenocrysts, mostly altered to calcite, muscovite, etc., 

 seem to have been originally soda-lime feldspar. The ground- 

 mass is a finegrained aggregate, consisting chiefly of quartz, 

 orthoclase, and muscovite. In the fresher scapolite pheno- 

 crysts the cross sections are sometimes rectangles, but the 

 favorite occurrence is in the form of a penetration twin of two 

 such crystals along the composition plane 110 ; and the corners 

 of the pinacoids whose faces constitute the rectangles are trun- 

 cated by the prism. There are no true longitudinal sections 

 in the slide, all being of small double refraction and having 

 approximately the same orientation. 



Occurrence of Scapolite Hocks elsewhere. 



The scapolite rock from ISTorway in the vicinity of Oede- 

 garden has been described by Brogger and Reusch. This rock 

 is essentially a mixture of scapolite and amphibole with acces- 

 sory titanite, and was regarded by the describers as a facies of 

 the gabbro (hyperite) in the neighborhood of veins of apatite 

 which traverse the gabbro. The observers concluded, more- 

 over, that the scapolite rock was formed by the alteration of 

 the normal hyperite or gabbro, since they found remnants of 

 diallage in the hornblende, as if the former were the original 

 mineral, and of plagioclase in the aggregates of scapolite, as if 

 the scapolite had formed from the plagioclase. The altera- 

 tion, according to Brogger' s view, was due to gaseous or jpneu- 

 matolitic action.* 



In Canada, also, granular rocks containing scapolite have 

 been described from a number of localities.f In one of these 

 rocks the principal constituents are pyroxene, hornblende, and 

 scapolite, with accessory epidote, enstatite, pyrrhotite, and 

 rutile, and the rock is classified as a scapolite diorite, it having 

 a granular structure. Another rock is made up of an aggre- 



*See Rosenbusch's Hikroscopische Physiographie der Massigen Gesteine, vol. 

 i, p. 331. 



f On some Canadian rocks containing scapolite. etc., by Frank D. Adams and 

 Andrew C. Lawson: Canadian Rec. Sci. 



