72 



NEW YORK STATE MUSEUM 



The North River Garnet Co. has opened a new deposit on Thir- 

 teenth lake, 7 miles southwest of North River, which was operated 

 for the first time during the past year. A large mill has been 

 erected near the mine. The old workings in the town of Minerva, 

 just west of North River, have been abandoned. The garnet of 

 the former locality occurs in a basic rock which appears to belong 

 to the gabbro series and thus differs in its association from the 

 usual occurrences in that vicinity. The principal constituents are 

 lime-soda feldspar and hornblende. The feldspar belongs to a basic 

 variety of plagioclase, probably anorthite. Orthorhombic pyroxene 

 (bronzite), biotite and small quantities of quartz are also present. 

 The pyroxene is largely altered to chlorite. 



The deposits on Gore mountain have been worked for many years 

 and are very extensive. They occur along the northern face of the 

 mountain at an elevation of about 2800 feet. They have been opened 

 at several points along the strike, but so far hardly more than the 

 superficial portions have been removed.- Their thickness exceeds 

 100 feet in places. H. H. Barton & Son is the only company that 

 operated at this locality during the year. 



On Garnet peak, a prominence about 3 miles from North River 

 on the road leading to Indian Lake, there are several mines that 

 are worked intermittently by small operators. 



Some interest has been shown during the year in a deposit of 

 different type than those described. The locality is on the eastern 

 slope of Mt Bigelow, 5^2 miles south of Keeseville, in northern 

 Essex county. The country rock is anorthosite, a part of the great 

 mass of that rock which is exposed in the central Adirondacks. It 

 is made up of granular feldspar with a little pyroxene, biotite and 

 garnet and has a more or less laminated appearance. In the vicinity 

 of the garnet deposit the rock shows considerable variation due to 

 included bands of amphibolite and pegmatite. The garnet does not 

 form crystals, but occurs in irregular and lens-shaped bodies of 

 massive character that are apparently in direct contact with the 

 anorthosite. Except for admixture with small greenish crystals 

 of pyroxene the garnet is quite pure. At one locality there is an 

 almost continuous series of outcrops extending north and south 

 for a distance of 400 feet. The greatest thickness shown is about 

 40 feet. The garnet usually has a finely granular texture and 

 readily crumbles under slight pressure, but occasionally it is platb- 

 and breaks with a smooth surface. Its origin is probably to be 

 explained by alteration, similar to that which has given rise to the 

 amphibolite bands, which have been caught up during the intrusion 



