Neplieline Rocks in Brazil. 287 



sahi " or violet-rock contains it as an essential component. This 

 is well developed near Tokusima, and its geological range has been 

 traced further. The piedmontite occurs in this rock along with fine 

 quartz-grains under a schistose arrangement, the accessories being 

 muscovite, greenish-yellow garnet, rutile, some felspars, iron- 

 glance, &c. 



The crystals of piedmontite are elongated, cracked, and much 

 striated, and occur with the orthopinacoid parallel to the planes of 

 schistosity. The crystal faces are, as a rule, well developed, thus 

 differing from common epidote, regarded as a rock-forming mineral. 

 Twinning is rare ; cleavages upon the base and orthopinacoid are 

 sometimes observed. The clino-pinacoidal sections of the mineral 

 show the most intense colours : the polarization-colours are magni- 

 ficent. The following is the analysis :— 



Si0 2 36-16 



A1 2 3 22-52 



Fe 2 3 9-33 



Mn 2 3 6-43 



CaO 22-05 



MgOK 2 0,Na 2 0-84 



FLO 3-20 



100-53 

 The chemist expresses a doubt as to whether the iron exists in 

 the state of sesquioxide or monoxide. The Author then alludes to 

 the difference of opinion as to the state of oxidation of iron in the 

 Swedish and Alpine piedmontites, and suggests that the Japanese 

 mineral supplies a missing link between the two. The Japanese 

 mineral was originally mistaken for tourmaline, and the rock called 

 Tourmaline-schist by E. Nauniann. Although comparatively rare 

 both in Piedmont and Sweden, in certain parts of Japan it is so 

 abundant as to constitute a rock-forming mineral, whilst as an 

 accessory it occurs also in the glaucophane-schist. 



The Author further describes a peculiar epidote, containing iron, 

 from the glaucophane-schist, and also a peculiar garnet, occurring in 

 rhombic dodecahedra about the size of a pea, which includes many 

 other minerals, but no glaucophane. The garnet is of a deep yellow 

 colour, and is anisotropic, a circumstance probably due to strain 

 from the interposition of other minerals. 



June 23.— Prof. J. W. Judd, F.R.S., President, in the Chair. 



The following communications were read : — 



1. " On Nepheline Rocks in Brazil, with special Reference to the 

 Association of Phonolite and Foyaite." By Orville A. Derby, Esq., 

 F.G.S. 



The Author refers to the phonolites and associated basalts of 

 Fernando Noronha, a deep-sea island off the north-eastern shoulder 

 of the continent of South America . Nepheline rocks of a somewhat 

 different character are abundantly developed on the mainland, and 

 under conditions favourable for throwing light on the relations 



