122 
ANNALS NEW YORK ACADEMY OF SCIENCES 
expected that some of these minerals would be of like origin, but such is 
rarely the case. As a rule they are minerals which are destructible by even 
a moderate heat (unless perhaps under pressure), 1 and most of them contain 
considerable water in their composition. 
Calcite, which is usually predominant among these minerals, occurring 
in rhombohedral, prismatic and scalenohedral crystals and in masses with 
rhombohedral cleavage, would be converted at a moderate heat into quick¬ 
lime. Gypsum, which contains about 20% of water, would be dehydrated 
into plaster of Paris. Thaumasite, which occurs liberally in some of the 
quarries, contains both of these minerals. Pectolite, which is of very general 
occurrence, contains from 3% to 9% of water and would be dehydrated. 
Quartz, which occurs as rock crystal and chalcedony, is disintegrated when 
heated, probably by vapor pressure generated from liquids in microscopic 
cavities. 
The zeolites proper, of which the crystals chiefly consist and which are the 
minerals more exclusively characteristic of the trap, would, as their name 
implies, fuse into shapeless masses. All contain water of crystallization. 
Many circumstances observed in the New Jersey localities seem to indicate 
that these minerals have been or are now being produced simply by crystalli¬ 
zation from solution, the solvent being probably water and the dissolved 
material, chiefly the trap rock itself. 
An average of four analyses, three by R. B. Gage 2 and one by L. C. 
Eakins 3 of the diabase of the Newark Formation from New Jersey localities 
near those productive of trap minerals, gives its composition approximately 
as follows: 
sio 2 
53.36 
A1A 
13.40 
Fe 2 0 3 
1.78 
FeO 
9.93 
MgO 
8.14 
CaO 
8.30 
Na,01 
k 2 o | 
3.49 
TiO z 
1.35 
p 2 o 5 
.27 
MnO 
.20 
100.22 
1 T. Graham: Elem. Inorg. Chem. Phil., p. 181. 1858. 
2 J. V. Lewis: N. J. State Geol. Survey Report for 1907, p. 121. 
3 F. W. Clarke: U. S. Geol. Survey Bull. No. 228, p. 47. Basalt from the Watchung 
Mountain, Orange Auvergnose. 
