4i8 REVIEWS 



Genesis of the Zinc Ores of Edwards District, St. Lawrence County, 

 NY. By C. H. Smyth, Jr. New York State Museum 

 Bulletin, No. 201. Albany, N.Y,, 1917. Pp. 39, pis. 12. 



This report presents the results of laboratory studies of ore from the 

 zinc deposits of the Edwards district, which is about 15 miles south of 

 the Canton area described in Bulletin 185, reviewed above, and the 

 geology of the two areas is very similar. The ore minerals are sphalerite, 

 pyrite, and galena, and occur as fillings of narrow cracks or as replace- 

 ments along shear zones in the Grenville crystalline limestone. The 

 deposits are of the high-temperature t5^e, and the sequence of mineral 

 deposition is as follows: (i) diopside, tremoUte, (2) pyrite, (3) sphalerite, 

 (4) galena, (5) talc, (6) serpentine. This sequence of mineral deposition 

 indicates changing conditions from intense-contact, metamorphic con- 

 ditions to those normal for the depths involved and without outside 

 agencies. At all stages during this transition from intense to moderate 

 conditions calcite was subject to repeated solution and recrystallization. 



The granite magmas which intrude the Grenville sediments are 

 considered the source of the ore minerals and during the cooling of the 

 magma, gases and solutions were given off which carried the sulphur 

 and metals into the country rocks where they were precipitated. The 

 wall rock of the sphalerite is always crystalline limestone while the 

 typical pyrite ore is always in schist or gneiss. Also the pyrite ore is 

 always rich in graphite while the zinc ore contains but little graphite. 

 The typical pyrite ore contains but little sphalerite but the zinc ore 

 contains considerable pyrite. 



These deposits are compared with zinc deposits of other regions and 

 especially with the contact zinc deposits of the Christiania district 

 described by Goldschmidt. Excellent photomicrographs show clearly 

 the various mineral relations described in detail in the text. This is a 

 valuable contribution to the subject of contact metamorphic ore 

 deposits. j_ ^ yj^ 



New Edition of Coal, Oil, Gas, Limestone, and Iron Ore Map. West 

 Virginia Geological Survey. 



Thoroughly revised, showing oil and gas pools, many anticinal lines 

 not heretofore shown, and also booklet giving the names and post-office 

 addresses of all the principal coal-mining operators in West Virginia up 

 to July I, 1921. Scale, 8 miles to the inch. Price, folded in strong 

 envelope and delivered by mail, $1.00. Remittances to West Virginia 

 Geological Survey, Box 848, Morgantown, West Virginia. 



