184 BULLETIN 131, UNITED STATES NATIONAL MUSEUM 



covered with overwash from the mountain slope, but in places 

 outcropping several feet high. The width is approximately 150 

 feet and the rock is full of opals of all sorts— milky, blue, green, 

 brown, pink, etc., and among them some perfectly transparent fire 

 or flame opal. Many of the masses are large, but to obtain good 

 sized stones from them is difficult as the opals are very brittle and 

 the rock is very hard. The locator obtained one stone of 60 carats 

 which showed green reflections and a brown opal of 150 carats, but 

 otherwise no good stones above 10 carats weight. The opal here 

 is largely of the glassy variety with broad flames of color, but it is 

 fragile and not well suited for jewelry. There is a large proportion 

 of loss by breakage. 83 Umpleby mentions this locality as on Panther 

 Creek in the eastern part of the Gravel Range district. He states 

 that the opal occurs as linings in the vesicles of rhyolite flows but 

 that precious opal does not appear to be present in commercial 

 quantities. 84 



LINCOLN COUNTY 



Very fine specimens of very well preserved opalized wood are 

 widely distributed in collections labeled as from Clover Creek, 

 Lincoln County. The material is buff to yellow and black in color 

 and is remarkable for the perfect preservation of the grain and 

 original structure. Specimens of polished cross sections preserved 

 in the National Museum are shown in plate 4. No data are available 

 as to the occurrence of this material, which was originally collected by 

 Otto Uhrlaub, of Bliss. Dr. Frank H. Knowlton reports that the 

 wood is all of a dicotyledonous tree, quite certainly oak, and is 

 probably late Tertiary in age. It is quite possible that the material is 

 from Miocene lake sediments. 



OWYHEE COUNTY 



Opal has long been known to occur in Owyhee County. In 1893 

 it was said that the Owyhee opal mines were situated on section 

 13, township 1 north, range 4 west, Boise meridian, about 3 miles 

 from Snake River in Owyhee County. The work done on the 

 mine amounted to about 8 months work for 2 men. The opal 

 taken out amounted to about 7,000 carats in the rough, varying 

 from transparent fire opal to the finest noble white opal; but nearly 

 all of this was either given away or poorly marketed. The opals 

 were said to occur in a nearly vertical dark andesite dike about 25 

 feet wide which outcropped for a distance of 750 feet. In the center 

 this contained a layer of very hard jasper 4 to 5 feet wide on each 

 side of which the opals occurred in seams and flat pockets. The 



83 Geo. F. Kunz. Mineral Resources, United States Geol. Survey, 1902, p. 853. 

 8< Joseph B. Umpleby. U. S. Qeol. Survey, Bull. 528, p. 174, 1913. 



