178 H. B. PATTON TOPAZ-BEARING KHYOLITE, UTAH 



furnished as io the actual environment and as to the conditions under 

 which they were formed. An opportunity to study the crj^stals and the 

 rocks in which they occur was afforded the writer by a visit to the locality 

 during the early part of last summer, and the observations made at that 

 time and a more leisurely study m^de of the large amount of material 

 collected furnish the excuse for this paper. 



The discovery of this topaz locality was first made hj Henry Engel- 

 mann, geologist of an expedition across the Great basin of Utah con- 

 ducted by Captain J. H. Simpson in the year 1859.^ 



This discovery of Engelmann appears to have been forgotten or over- 

 looked, probably because of his rather vague description of the locality. 

 In 1884, however, the same locality was visited by Professor J. E. Clay- 

 ton, of Salt Lake City, and numerous specimens collected. Since that 

 time many others have Journeyed to the place for the purpose of collect- 

 ing the crystals. 



In 1886 Whitman Cross published a very brief description of the topaz 

 crystals of the Thomas range and of the rock in which they occur. Mr 

 Cross, however, did not visit the locality, but was indebted for the scant 

 material at his service and for information concerning it to the kindness 

 of Professor Clayton. His description is quite accurate, so far as his 

 information went, and is given in connection with a fuller description of 

 a very similar occurrence at Nathrop, Colorado, in a paper entitled "On 

 the occurrence of topaz and garnet in lithophyses of rhyolite."* 



A further very brief description of this occurrence has been furnished 

 by Arthur J. Jones, who visited the place in 1891.'^ 



Further brief mention of these topazes, aside from the communication 

 by A. IST. Ailing, as given above, are made by G. F. Kuntz" and by 0. C. 

 Farringion,^ who gives an excellent colored illustration of the wine- 

 colored crystals clustered in a lithophysal cavity. 



Location 



The exact locality in which these topaz crystals are found is in one of 

 the desert ranges of Utah designated by Clayton the Thomas range and 



' Report of explorations across the Great basin of the Territory of Utah, etcetera, by 

 Captain J. H. Simpson, Engineer Department, U. S. Army. Washington, 1876, p. 324. 



4 American Journal of Science, vol. 31, 1886, p. 432. 



° Topaz crystals of Thomas mountain, Utah. Proceedings of the Iowa Academy of 

 Science, vol. 2, pp. 175-177. 



U. S. Geological Survey, mineral resources, 1883-1884, p. 738 ; U. S. Geological Sur- 

 vey, mineral resources, 1892, p. 764. Gems and precious stones, p. 67. New York, 

 1892. 



'Gems and gem minerals, p. 121. Chicago, 1903. 



