REPORT OF THE DIRECTOR AND STx\TE GEOLOGIST 1903 161 



very basic eruptive rock changed by metamorphism to its 

 present state.^ 



The garnet occurs in masses of varying size, from pieces the 

 size of an egg to masses having a diameter of 20 feet and more. 

 The various qualities are distinguished commercially as massive 

 garnet, shell garnet and pocket garnet. The massive garnet is 

 very impure from the presence of oither minerals. The shell 

 garnet is the almost pure material and is the most desirable 

 for industrial purposes. The pocket garnet occurs in small 

 accumulations, incipient crystals, in the gneiss.^ This Adiron- 

 dack material, though of the common variety almandite, is how- 

 ever extremely hard, its hardness being 8., v^hich is from 1.5 to 

 .5 harder than the general hardness of this variety. Its popular- 

 ity among garnet paper manufacturers is due to this extra 

 hardness and a tendency to cleave more easily than other oc- 

 currences of the same variety. 



Methods of extraction and preparation 



The garnet is mined entirely by open cut work and was 

 formerly picked out by hand. By this process only the very 

 richest beds could be worked, and the decomposed surface por- 

 tions usually determined the extent to which the deposit could 

 be developed. The best garnet in the solid rock was left and 

 covered over by the debris from the working of the surface 

 material. In 1899 a new mechanical process was established by 

 Mr F. C. Hooper, of the North Kiver Garnet Co. of North River, 

 Warren co., by which the rock was broken down by steam drills, 

 crushed and the garnet concentrated by gravity. By this 

 method, garnet, 95^ pure, is obtained, an increase in purity of 

 from 25^ to 45^ over the old method of hand-picking. This 

 degree of concentration is remarkable when the difference in 

 specific gravity between the minerals to be separated is less 

 than .5. Specimens of pure garnet and pure hornblende from 

 the North River Grarnet Co.'s mines gave specific gravities of 3.2 



^Min. Ind. 1898. 6:20. 



'N. Y. State Mus. Bui. 15. 1895. p. 553. 



