602 THE JOURNAL OF GEOLOGY. 



eruptives in these collections suggested a comparison with the 

 Tingua and Cabo Frio monchiquites, and Mr. Bauer was requested 

 to search for the characteristic rocks of these places, specimens 

 being sent him for comparison. The return mail brought typical 

 specimens of foyaite, and with this indication of a new locality 

 for that rock, and in the hope of being able to study the Ipanema 

 ore deposit more advantageously at another place, an excursion 

 to Jacupiranga was resolved upon. Under the guidance of Mr. 

 Bauer, and aided by subsequent investigations by him and Dr. 

 Eugen Hussak, the district was found to consist essentially of 

 jacupirangite cut by dykes of foyaite with which is associated 

 phonolite, various types of augite-syenite and a micaceous pyrox- 

 ene-plagioclase rock in such a way that there is no escaping the 

 conclusion of a genetic relation between these various types. 

 Outlying dykes of the plagioclase rock assume in one place the 

 characters of a gabbro, in another, those of a teschenite. Among 

 the outlying dykes of the district are various types of basic 

 eruptives, including leucite-basanite, vosgesite and syenite- 

 porphyry whose relations to the eruptive center are less clear, 

 but which are also suspected to be genetically connected with 

 the nepheline-bearing types. Most interesting is a cryptocrys- 

 talline orthoclase-pyroxene rock passing to coarse grained augite- 

 syenite and presenting a tuffaceous facies clearly indicative of 

 volcanic action. 



With the clues obtained at Jacupiranga the study of Ipanema 

 became comparatively easy. The jacupirangite type passing to 

 an iron ore was found as a dyke with the facies of a breccia at 

 the margin, traversing decomposed rock which is evidently iden- 

 tical with the compact augite-syenite of Jacupiranga. By dili- 

 gent search the latter was found in a sound condition and pre- 

 senting a variety of interesting phases, such as a passage to coarse 

 grained augite-syenite, tuffs identical with those of Jacupiranga 

 and, most interesting of all, a basic facies in which the orthoclase 

 is replaced by phosphate of lime in the form of apatite. A sin- 

 gular mode of occurrence, and one bearing directly on the ques- 

 tion of consanguinity, is that of micro and macroscopic inclusions, 



