286 UNIVERSITY OP VIRGINIA PUBLICATIONS 



Norway. In 1890, Nason and Ferrier* published a brief account of a 

 massive igneous rock, corresponding in composition to hornblende granite, 

 from the Archaean highlands of New Jersey, in which zircon was a promi- 

 nent constituent of the rock, amounting in some specimens to nearly 20 per 

 cent, with a probable average of 5 per cent. The zircon crystals ranged 

 in size up to 25 mm. in length, with an average of about 5 mm. Mention 

 was made by Cookf in 1868 of a zircon-bearing gneiss at Trenton, New 

 Jersey. 



Sedimentary rocks. ThiirachJ found zircon in sands, sandstones, con- 

 glomerates, and carbonate rocks (limestone and dolomite) of different 

 ages. He reported it present in every sandstone and in nearly every shale 

 examined. Adams and Barlow§ report large roimded grains of zircon in 

 thin scales of impure limestone in the township of Dudley, Canada, and at 

 Warwick, New York, in limestone and scapolite.lJ Derby" has noted that 

 zircon is essentially absent from argillaceous deposits, and Clarke's® com- 

 posite analysis of 78 shales shows no zirconium. Its density would proba- 

 ably cause it to settle with the sands and not be transported to the quieter 

 waters in which shales are deposited. 



Because of its resistance to atmospheric agencies zircon is a frequent 

 associate in beds of sand and gravel, and in the residual decay derived from 

 the weathering of crystalline rocks in which it originally occurred. In 

 each of the Atlantic States containing areas of crystalline rocks it has been 

 noted in association with many other heavy resistant minerals derived from 

 the rocks by the usual processes of decay. 



Numerous references in the literature are made to the abundant occur- 

 rence of zircon in the gold sands of the Piedmont region of the Southern 

 Appalachians, especially of the Carolinas. It is a common constituent in 

 the alluvial gold sands of the eastern and western United States, and of 

 foreign countries ; in the diamond sands of Brazil ; in the monazite sands of 

 the Carolinas; of Sweden, Norway, Australia, India, and the beaches of 

 Brazil, where partial concentration from the action of tides and waves has 

 taken place; in the gem sands of Ceylon; in the northwestern alluvial tin 

 mines of Tasmania; and in the tin placers of the Malay Peninsula. 



* Nason, F. L., and Ferrier, W. F., A Notice pf Some Zircon Rocks in the Archaean 

 Highlands of New Jersey, Amer. Asso. Adv. Sci., 1890, p. 244 (Abstract), 

 t Cook, G. H., Ann. Rept. State Geol. Survey of New Jersey, 1868, p. 323. 

 t Thiirach, H., Op. cit., pp. 18-19. 



§ Adams, F. D. and Barlow, A. E., Memoir 6, Geol. Surv. of Canada, 1910, p. 216. 

 If Dana, E. S., Op. cit., 1900, p. 485. 



° Derby, O. A., Proc. Rochester Acad. Sci., 1891, vol. i, pp. 198-203. 

 O Clarke, F. W., Op. ci7., p. 28. 



