LEVISON, NEWARK IGNEOUS ROCKS 
127 
likely, however, that their production is chiefly due to chemical reactions 
resulting in the formation of less, from more soluble substances in solution. 
Several crystallized minerals, including some zeolites, have been arti¬ 
ficially produced from aqueous solution, both accidentally and intentionally. 1 
That water percolating from above is concerned in the production of 
the New Jersey trap minerals appears to be indicated by the circumstance 
that crystals which occur on the upper sides of cavities are usually unim¬ 
paired, even though colored, while those which occur on the under sides have 
usually occluded a sedimentary material resembling yellow or red oxide of 
iron or a ferruginous clay in fine particles, which also frequently covers them 
with a coating evidently imbedded in the surface and impossible to remove. 
Clusters of crystals projecting from the sides of cavities are frequently thus 
coated on the upper, while unsullied on the under surfaces, a circumstance 
of common occurrence with calcite and prehnite. The lustrous under¬ 
surface of such an occurrence of reniform prehnite is shown in Plate XI, 
Fig. 2. The material of this coating, which is also often occluded through¬ 
out a crystal, consists perhaps of the 2% to 3% of ferric iron with other 
undissolved residues of the trap and some clay from the top soil all carried 
down mechanically by the water. It sometimes has a bright red color as 
though chiefly a ferric compound, thus occurring on crystallized quartz and 
heulandite at West Paterson and stilbite and heulandite at Upper Montclair, 
common, and on heulandite at Great Notch, rare. 
Spring water would act upon the trap somewhat differently from rain 
water for several reasons, and coming perhaps through various other rocks 
before entering the trap may so acquire the boric acid and fluorine required 
and be accountable for the production of datolite, which occurs liberally in 
some quarries and contains the large proportion of 21% of boric acid; and 
also such apophyllite as contains fluorine. 
Release of pressure may account for the deposition by spring waters of 
such crystallized minerals in the trap, as it does for the escape of gases and 
the deposition of sulphur from sulphur waters, iron carbonate and oxides 
from chalybeate waters, and calcareous and siliceous sinters from hot-spring 
waters. 
The microscopic crevices through which the water enters cavities in the 
rock are often disclosed at Great Notch, N. J., by the sledge hammer. 
Large yellow calcite crystals somewhat resembling those of Joplin, Mo., 
occur there in such cavities, but any attempt to trim the rock away around 
such a crystal usually results in its splitting directly through the cavity and 
the destruction of the crystal. The parted sides of the split are often covered 
1 J. P. Iddings: op . cit ., p. 96. 
