220 Mineralogy and Geology of St. Lawrence Co., N. I 



Art. HI. — Essay on the Mineralogy and Geology of St. Lawrence 

 County, State of New YorJc; by J. Finch, F.B.S., he. 



The northern part of the State of New York, bordering on the 



river St. Lawrence, has rarely attracted the notice of the mineralo- 

 gist. 



I was invited by Jacob A. Vanden Heuvel, Esq. during the sum- 

 mer of 1830, to pass a few weeks at his residence at Heuvel, a flour- 

 ishing village near Ogdensburg, and took advantage of the opportu- 

 nity to make some excursions in the vicinity. The result has been 

 the discovery of some new localities of minerals, which may be in- 

 teresting to those who are pursuing that department of natural science. 

 Among the bowlders scattered over the' surface of the fields, there 

 may be observed, granite, porphyritic granite, and gneiss. They 

 have their angles rounded, but are not of very large size. Most of 

 these differ in general character and appearance, from the primitive 

 rocks found at the south of the county, and we must therefore refer 

 their origin to the rocks of Canada. At Laurentia, the seat of Mr. 

 Vanden Heuvel on the St. Lawrence, there are numerous massy 

 bowlders, composed of Labrador felspar, hornblende, and glassy fel- 

 spar, thus forming a rock which has not, I believe, been found in any 

 other part of the United States. Masses of sandstone, and transition 

 quartz rock, also occur on the surface, but their angles are not roun- 

 ded, and they are evidently derived from the immediate neighbor- 

 hood. Among the few minerals which occur in the loose bowlders 

 are pargasite, augite and resplendent hornblende. 



The formation at Heuvel, which also extends across the whole of 

 the County, is granular quartz rock, composed of grains of quartz, 

 cemented by decomposing felspar. A small quantity of alumine 

 is sometimes united to the quartz. It is usually of a grayish white 

 color, sometimes reddish white. Occasionally it is full of small cav- 

 ities, which give the rock an honey comb appearance. It occurs in 

 strata, varying in thickness from a kw inches, to two feet. It lies 

 nearly horizontal, the inclination in no instance near Heuvel, being 

 so much as 10°. Sometimes the rock is covered with very minute 

 crystals of pure quartz. This formation must be referred to the 

 transition series, on account of its horizontal position,* and because in 



An indecisive character. — Editor. 



