THE MINING AND QUARRY INDUSTRY I913 'JJ 



GRANITE 



Granite is both a specific and a general term. When used in 

 the restricted scientific sense it means an igneous rock of thor- 

 oughly crystalline character in which the chief constituents are 

 feldspar, quartz and mica. Such a rock has a massive appearance, 

 that is, the constituents are uniformly distributed in every direction, 

 and owing to the predominance of the feldspar and quartz, the 

 color is rather light, commonly gray or pink. As a variation to 

 the uniform distribution of the minerals, the latter may develop a 

 plane parallel arrangement through the influence of compression 

 when the mass was still deeply buried in the earth's crust. A 

 granite with this parallel or foliated texture is known as a granite 

 gneiss. 



The commercial definition of granite is much broader than that 

 given and includes almost any of the crystalline silicate rocks 

 (usually igneous) that possess the requisite physical qualities for 

 use as architectural or monumental stone. In most cases the com- 

 mercial product is actually a granite in the true sense, but not in- 

 frequently it may be a syenite which lacks quartz, or a diorite 

 consisting of plagioclase, feldspar and hornblende, or anorthosite 

 which contains little else than basic plagioclase feldspar. So-called 

 black granites are mainly gabbros and diabases with a large pro- 

 portion of the iron compounds pyroxene, hornblende and magnetite. 



The broader usage will be followed in the present classification, 

 as all the above named rocks are quarried in this State. The 

 only silicate rock not included under granite is diabase or trap 

 which, on account of the special features surrounding its production 

 and uses, is classed by itself. 



Granites and the related igneous types are restricted to two 

 well-defined areas in New York — the Adirondacks in the north 

 and the Highlands in the southeast. Some account of the principal 

 quarries in the two areas has been given in the issue of this report 

 for the year 191 1. 



The production of granite in the last three years is shown in 

 the accompanying table. The figures represent the commercial 

 value of the output of all quarries with the exception of those, 

 operated by contractors on road improvement work, for which it 

 is very difficult to compile any reliable figures. The total value of 

 the granite quarried in 1913 was $335,642, as compared with 

 $202,096 in 19 1 2. The gain was mainly in the item of crushed 

 stone. There was little change in the building, monumental and 

 other kinds, aside from the crushed product. 



