THE MINING AND QUARRY INDUSTRY I914 69 



MARBLE 



Marble, in the commercial sense, like granite, includes a variety 

 of rocks that lend themselves to building or decorative uses. Most 

 commonly, the name signifies a crystalline aggregate of calcite or 

 dolomite, as distinguished from ordinary limestones which at best 

 are of indistinctly crystalline nature. At the same time it implies 

 the feature of attractiveness by reason of color and the ability to 

 take a lustrous polish. Rocks possessing all these features are 

 marbles in the strict sense to which the name may be applied with- 

 out qualification. Some compact or granular limestones that lack 

 the elements of thorough crystallinity make, however, a handsome 

 appearance when polished, and such are commercially classed as 

 marbles. Fossil marbles, black marbles, and a few other kinds are 

 commonly of the noncrystalline type. Serpentine marble, or verde 

 antique, is made up for the most part of the mineral serpentine, 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 mass and the greenish 

 serpentine inclusions. 



Marbles belonging to those various types find representation in 

 the geologic formations of the State and are quarried on a commer- 

 cial 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 dis- 

 turbance and metamorphism which in the Adirondacks was brought 

 to a close practically before Cambric time and which in southeastern 

 New York was completed in the Paleozoic. This thoroughly crys- 

 talline 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 lime- 

 stones 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 



