ERBE INS TIPUTE O SOMENCE 
MINERALOGY OF THE NEWARK GROUP IN PENNSYLVANIA 
datolite, and gave 0.165% B,O,, and the other showed a number of small bub- 
bles filled with calcite and chlorite and gave 0.140%. In order to determine if 
possible the form in which the boron was present in these samples, they were 
treated with a heavy solution, acetylene tetrabromid, diluted with benzene. 
After several trials it was found that the boron mineral in both cases had a 
specific gravity of 2.8. As this mineral was further completely soluble 
in hydrochloric acid, there can be little doubt that it represents datolite, which 
in the first, has in part penetrated into the rock, as well as depositing in the 
cavity, and in the second, may well be present in some of the amygdules, but 
obscured by the more abundant calcite. The intrusive sheet proved entirely 
free from boron throughout its extent. 
With a view to determining if similar relations existed elsewhere, attention 
was turned to the occurrence of boron minerals in other trap masses in Penn- 
sylvania, and the sheet which crosses the Delaware River below New Hope, in 
'astern Bucks County, was studied in a similar manner. This sheet is of typical 
intrusive character, as is proved by the intense metamorphism of the sedimentary 
rocks overlying it, and by its coarse diabasic texture, without the slightest de- 
velopment of glass or of steam-bubble cavities, even at its uppermost surface. 
The intensely altered shale immediately above the contact, as exposed 
along the river road, contains an abundance of minute crystals of black tourma- 
line, of peculiar lenticular shape, owing to the practical absence of faces in the 
prismatic zone; these become less frequent upwards, and at thirty feet above 
the trap disappear altogether, although alteration is evident through a thickness 
of over 1500 feet of shale. The amount of tourmaline present in a specimen 
obtained from as near the contact as possible was roughly estimated at one per 
cent, which would correspond to o.1 per cent of B,O,, and analysis actually 
gave 0.105%. In a specimen from a distance of twenty-five feet above the 
contact 0.005% was found; while in the altered rocks from still higher hori- 
zons none could be detected. This tourmaline can certainly not have been 
produced by any weathering process, but must have been developed by the 
action of the intrusive trap, and its limitation to the lower 30 feet of altered 
shale indicates that the source from which the boron entering into its com- 
position came could have been no other than the molten magma itself. 
The trap at the contact was next investigated, and boron was found to 
be entirely absent from it, as from the traps at Jacksonwald, showing that this 
element must have been totally expelled during the crystallization of its constituent 
