Granite at Mounts Adam and Eve. 64Y 



met (slide 150). The section proved to be approximately perpen- 

 dicular to the acute bisectrix, and the plane of the optic axes in 

 one-half of the twin made an angle of about 34° with the trace of 

 the twinning plane, and in the other half about 44°, but in the same 

 sense as that of the first half, placing thus the two planes of the 

 optic axes at 10° with each other. The alteration yields an iso- 

 tropic aggregate, in which the fresh kernels are embedded, and the 

 whole effect is very like that of altered olivine. Specimens from 

 the farm of Mr. E. Green, southeast of Mt. Eve, from a prospect 

 that had been dug for minerals, proved to contain the usual contact 

 mixture of silicates, etc., including hornblende, biotite, titanite, 

 scapolite, and with these leucopyrite, well known from this region 

 (slides 100-103). The small granite exposures northwest of Amity, 

 on the land of Mr. D. Knapp, exhibited in section the usual malaco- 

 lite, plagioclase, a little orthoclase, and a fine rutile crystal. While 

 the neighboring limestone showed the usual silicates. 



In resume of these contacts it may be said that the granite be- 

 comes much richer in pyroxene (malacolite) as they are approached, 

 but it shows no developments of porphyritic structure, so that vre 

 are justified in concluding that we have to do with a plutonic mass. 

 Along the contact is the scapolite zone, consisting of coarsely crys- 

 talline scapolite and malacolite. Next comes the coarsely crystal- 

 line limestone charged with the aggregates of silicates so often 

 mentioned above. These are oftenest in bunches and knobs, but 

 also appear in general dissemination in many places. The presence 

 of chondrodite and fluorite, with their percentages in fluorine, is 

 worthy of comment in these surroundings. The rare borotitanate 

 of magnesia and iron, warwickite, that has been found near Amity 

 is also not to be overlooked, as containing boracic acid, a charac- 

 teristic associate of granite contacts. The following additional con- 

 tact minerals have been noted by collectors of minerals — vesuvian- 

 ite, tourmaline, and corundum. 



Mineral aggregates in limestone, along igneous contacts, and 

 similar to those described above, are known elsewhere in this 

 country, and have been described from several European sources. 

 In the prolongation of this white limestone belt into New Jersey, 

 F. L. Nason has recorded the presence of the scapolite rock as a 

 contact phenomenon of granite.^ Its mineralogy, as determined by 



1 Annual Report State Geologist of N. J., 1890, p. 32. 



