HOBBS — MINERALOGY OF WISCONSIN. Ill 



T. C. Chamberlin, The Ore Deposits of Southwestern 

 Wisconsin. Geology of Wisconsin, Vol. IV, pp. 377-398. 



(1882.) 



R. D. Irving, Minerals of Wisconsin. Ibidem, Vol. I, 

 pp. 309-339. (1883.) 



George F. Kunz, (Note on finding of Eagle Diamond). 

 Mineral Resources of the United States for 1883 and 1884, 

 p. 732. (1885.) 



George F. Kunz, On the Occurrence of Diamonds in Wis- 

 consin." Bull. Geol. Soc. Am., Vol. 2, pp. 638, 639. (1891.) 



E. S. Dana, Catalogue of American Localities of Min- 

 erals. System of Mineralogy, 6th Ed., p. 1087. (1892.) 



Wm. P. Blake, The Mineral Deposits of Southwest Wis- 

 consin. Trans. Am. Inst. Min. Eng., Chicago Meeting, 

 pp. 1-11. (1893.) 



Wm. H. Hobbs, On a recent Diamond Find in Wisconsin 

 and on the Probable Source of this and other Wisconsin 

 Diamonds. American Geologist, Vol. XIV, pp. 31-35. 

 (1894.) 



THE CRYSTALLIZED MINERALS FROM THE PRE-SILURIAN 

 FORMATIONS OF SOUTHERN WISCONSIN. 



Quartz Crystals from Devil's Lake. — The fissures in the 

 Upper Huronian Quartzite of Devil's Lake, near Baraboo, 

 are frequently found to be lined with crystals of quartz, 

 which though quite small are very clear and have faces 

 well fitted for measurement. The occurrence of crystallized 

 quartz in the vicinity of Devil's Lake has been mentioned 

 by Irving in a paper entitled "Minerals of Wisconsin."' 

 These crystals are fully as limpid as the well known quartzes 

 from Herkimer county. New York. A crystallographic 

 study has been made of them on material recently collected 

 at Devil's Lake by Professor Van Hise. The crystals have 

 an average length of 3-6 "'" and a thickness of 1-2 """• 

 They have generally a marked trigonal habit occasioned by 

 the unequal development of alternate faces of the prism, 

 and by the subordination of the form z to r." Besides the 



1 Geology of Wisconsin, Vol. I, p. 318, isas. 



2 Throughout this paper the lettering of known planes agrees with that used by Dana in 

 the 6th edition of the System of Mineralogy. In one or two cases the lettering used by 



