GEOLOGY OF THE SCHROON LAKE QUADRANGLE 99 



granite and hornblende gneiss. Hornblende gneiss is all shot 

 through by pink granite, and the magnetite occurs as small, irregu- 

 lar masses through the mixture. 



Road Materials 



So-called " trap rock " is typically represented by the diabase 

 dikes of the quadrangle. Such rock ranks among the very finest 

 of all natural road-building material because of its hardness, fine- 

 ness of grain, homogeneity, freedom from mica, and good binding 

 power, this last being due to richness in iron-bearing minerals. 

 None of the diabase dikes of the quadrangle has ever been worked 

 though two of them, northwest and southwest of Schroon Lake 

 village (see map), are large and well located for quarrying purposes. 



The gabbro stocks, especially those free from mica, would fur- 

 nish a large amount of hard, homogeneous road material with good 

 binding power. None of these stocks has been quarried, though 

 some of them are very favorably situated with reference to promi- 

 nent highways. 



Rocks of the syenite-granite series, particularly those portions 

 free from mica, also yield a good quality of road material where 

 an artificial binder such as tar is used. There is practically no 

 limit to the available quantity of such rocks, though only two quar- 

 ries for road material have been opened in them. One of these 

 (with a smaller one close by) is in syenite by the state road one- 

 half of a mile east-northeast of South Schroon, and the other is 

 in granite near the state road one-half of a mile north of Mox- 

 ham pond. 



The quarry in the Little Falls ( ?) dolomite in Schroon Lake 

 village has been operated for road material. 



In several places small quarries or pits are located in disinte- 

 grated, coarse, crystalline Grenville limestone. This material, which 

 is gravelly and readily dug out, is used for local road repairing. 

 Among such small quarries are those near the road one-half of a 

 mile southwest of Olmstedville, and i mile northwest of 

 Olmstedville. 



Building Stone 



Building stones of fine quality occur in practically inexhaustible 

 amounts within the quadrangle. The members of both the anor- 

 thosite and syenite-granite series would rank as very strong, dur- 

 able, often beautiful building stones. In a few places very small 

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