THE MINING AND QUARRY INDUSTRY IQI2 79 
a silicate of magnesium and iron, and is therefore not related to 
the varieties already described. Ophitic limestone, or ophicalcite, 
is a crystalline limestone or dolomite carrying grains and nodules 
of serpentine scattered more or less evenly through its mass. Its 
ornamental quality lies in the speckled or mottled pattern and the 
sharp contrast between the clear white ground mass and the greenish 
serpentine inclusions. 
Marbles belonging to these various types find representation in 
the geologic formations of the State and are quarried on a com- 
mercial scale or have been so quarried in the past. 
The true or crystalline varieties are limited in occurrence to the 
metamorphic areas of the Adirondacks and southeastern New York. 
They are of early geologic age, antedating the period of crustal 
disturbance and metamorphism which in the Adirondacks was 
brought to a close practically long before Cambric time and which 
in southeastern New York was completed in the Paleozoic. This 
thoroughly crystalline character is in fact a development of the 
strong compression accompanied by heat to which they have been 
subjected; having been originally, no doubt, ordinary granular or 
fossiliferous limestones similar to those so plentifully represented 
in the undisturbed formations outside the regions. 
The crystalline limestones of the Adirondacks are most abundant 
on the western border in Jefferson, Lewis and St Lawrence counties 
where they occur in belts up to 4 or 5 miles wide and several times 
as long, interfolded and more or less intermixed with sedimentary 
gneisses, schists and quartzites. They are found in smaller and 
more irregularly banded areas in Warren and Essex counties on 
the eastern side, but have little importance elsewhere. The ophitic 
limestones that have been quarried at different times belong to the 
same series. The marbles of the Adirondacks comprise both the 
calcite class with very little magnesia and the dolomite class con- 
taining high percentages of magnesia. No definite relation is ap- 
parent in regard to the occurrence of the two and. both may be 
found in the same area and in close association. 
The southeastern New York marbles occur in belts which follow 
the north-south valleys, east of the Hudson, from Manhattan island 
into Westchester, Dutchess and Columbia counties. They range 
from very coarsely crystalline to finely crystalline rocks, are prevail- 
ingly white in color and belong to the dolomite class. They are 
interfolded with schists and quartzites, the whole series having steep 
dips like those of strongly compressed strata. The geologic age 
