212 DerTjij — Occurrence of Monazite in Iron Ore, etc. 



or of the rounded grains in which the mineral usually appears, 

 the monazite seems to be in a state of strain in virtue of which 

 it goes to pieces in the process of crushing and washing. On 

 testing in a borax bead the oxalates precipitated from a solu- 

 tion of the residue, Dr. Florence obtained beautiful crystalliza- 

 tions of both cerium and lanthanum, the latter appearing much 

 more abundantly and readily than in the many other samples 

 of monazite that he has examined in this way. From this cir- 

 cumstance it may be concluded that the mineral presents some 

 peculiarities of composition, but material is not at hand for a 

 verification of this point. 



The locality from which the specimen comes was visited in 

 1880 by Dr. Costa Sena, the present director of the School of 

 Mines of Ouro Freto, who reports the occurrence of loose 

 masses up to 100 kilograms in weight and of a vein from 

 half a meter to a meter in width in decomposed granitoid 

 gneiss in the bed of the Corrego do Emparedado, affluent of 

 the small river Sao Pedro, which enters the Jequitinhonha 

 from the left some 60 to 70 miles below the town of Calhau 

 (Arassuahy). An analysis made at that time gave 85^ of 

 carbon, 4*7^ of volatile matter and 7*2^ of ash. Judging from 

 the present specimen, which probably was about the same com- 

 position, the ash is composed for the most part of phosphates 

 of the cerium group in the form of monazite. 



Another specimen of graphite of similar appearance and 

 mode of occurrence, from near Sao Fidelis in the state of Rio 

 de Janeiro, presents the same phenomenon of an abundance of 

 monazite as the almost exclusive non-carbonaceous accessory. 

 On the other hand, several specimens of graphitic schist that 

 have been examined give an abundant residue of titanium 

 minerals (rutile in some cases, ilmenite in others), but no min- 

 erals of the rarer elements. This circumstance and the occur- 

 rence in the schistose types of graphite of a great amount of 

 sericitic mica indicates a difference in the mode of origin of 

 the two types of graphitic rock corresponding to the differences 

 in their mode of geological occurrence. Unfortunately no 

 specimens are at hand for verifying to what extent monazite 

 is a characteristic accessory of the graphite occurring in gneiss 

 and granite. As the two specimens examined, taken by chance, 

 have shown it in relative abundance, it may be suspected that 

 it will be found to be rather generally distributed. If so, 

 its significance from a genetic point of view hardly needs to be 

 mentioned. 



Sao Paulo, Brazil, December 24, 1901. 



