134 
ANNALS NEW YORK ACADEMY OF SCIENCES 
samples would obviously be necessary to serve as a basis for general con¬ 
clusions. 
As regards sequences these notes seem to indicate no conspicuously 
prevalent order in the genesis of the New Jersey trap minerals. 
Quartz, calcite and datolite appear to be, in the order named, most 
generally deposited first upon the trap. One or another of these three 
minerals usually thus prevails in a given quarry or part of a quarry at a 
given time; but in the same quarry at a later time, when a different texture 
of rock is in process of excavation, another of them may be the prevalent 
mineral thus deposited. Likewise, in two adjacent quarries or even parts 
of the same quarry the prevalent minerals differ considerably. Thus, 
datolite has been plentiful in one of the two adjacent quarries at Snake Hill 
and seldom found in the other. Again, in one of two adjacent quarries at 
Great Notch datolite in opaque crystals and prehnite in spheroids, both on 
crystallized quartz, were extremely prevalent and almost no thaumasite oc¬ 
curred. In the other quarry, now being actively worked, thaumasite is 
abundant and the above-mentioned combination rare or absent. In fact, 
the prevalent minerals often differ greatly as new mineral-producing rock 
areas but a few yards distant are reached. 
The minerals sequent upon datolite, calcite and quartz seem to be more 
numerous in the order named. Of the species which are more plentiful, 
apophyllite appears to occur upon the larger number of other species. 
Calcic sulphate not of frequent occurrence in the ordinary form of selenite is 
plentiful as a constituent of thaumasite. Conclusions in regard to sequences 
must, however, be only tentative until records of other localities are avail¬ 
able for reference. 
