CONSANG UIN1 TY OF ER UPTIVE ROCKS. 60 1 



sheets rather than dykes was found. A complete analogy, as 

 regards the essentially volcanic character of the massif, with the 

 Caldas region was thus established with the addition of evidence 

 of a lava-flow-like character in the foyaite masses*. (Quart. Jour. 

 XLVII., 1891). 



A chance fracture of a Caldas specimen showing obscurely an 

 appearance of dodecahedral faces on the external surface of the 

 singular polyhedral inclusions so characteristic of the two places, 

 suggested the search for partially decomposed material which by 

 cleaving around the inclusions would show their true form and 

 reveal the mystery of their origin. This search was rewarded 

 with the discovery of free masses of foyaite, like those of Magnet 

 Cove, Ark., having the external form of leucite. The presence of 

 such rock masses with crystalline outlines in both phonolite and 

 foyaite is another link in the chain of evidence of consanguinity 

 of foyaite, phonolite and leucite rocks, while the presence of 

 accessory plagioclase in some of these masses, taken in connection 

 with the occurrence already noted at Cabro Frio, suggests 

 another interesting line of investigation. 



Meanwhile another series of studies presented in an unexpected 

 manner certain new and interesting phases of the problem. Work 

 had been commenced on a deposit of magnetic iron ore at Ipanema 

 in the state of Sao Paulo where, from the extreme decomposition 

 of the rocks and other unfavorable circumstances, but little could 

 at first be made out beyond the association of the ore with a 

 peculiar clay made up in large part of scales of hydrous mica. 

 An ore of similar character at Jacupiranga in the same state was 

 being investigated by Mr. Henry Bauer, a German mining engi- 

 neer, and the collections sent by him showed the presence at that 

 place of an undescribed type of holocrystalline nepheline-pyrox- 

 ene rock since denominated jacupirangite, 1 which, by enrichment 

 in iron, passes to an iron ore, and, by secondary alteration of the 

 pyroxene, affords the same peculiar micaceous clay. Certain basic 



1 Am. Jour, of Science, XLL, 1891, p. 311. The same, or a very similar, type was 

 described simultaneously from Finland by Ramsay and Berghell with the name of 

 ijolith (Geologiska Foreningens i Stockholm Forhandlingar, No. 137, 1891). 



