176 BULLETIN 131, UNITED STATES NATIONAL MUSEUM 



vein of cellular quartz in andesite. On Summit Creek near where 

 the Ketchum-Mackay road crosses the divide fluorite occurs as 

 colorless to white octahedral crystals with platy pseudomorphous 

 quartz in talus slopes composed of Ordovician slate. 



Specimens of oxidized ore from the Pacific mine, Bay Horse 

 district, have small colorless to white cubic crystals resting upon 

 crusts of calamine. These were examined optically and found to 

 be isotropic with an index of refraction of 1.437 ±.002. These 

 properties identify the mineral as fluorite. This occurrence is 

 interesting as the fluorite is a very late deposit having formed sub- 

 sequent to the crystallization of the calamine. 



In the Stanley Basin district on Little Casino Creek the bedrock 

 contains a system of north-south fissures containing quartz and 

 a considerable amount of fluorite along one of which is a gouge seam 

 carrying gold. 68 



IDAHO COUNTY 



Purple fluorite has been reported to occur in very fine intergrowth 

 with quartz in a large low-grade pyritic gold lode at the Independ- 

 ence prospect in the Big Creek district. The best description of the 

 deposit available makes no mention of the mineral. 



OWYHEE COUNTY 



A specimen of ore from a stope in the east drift of the Silver City 

 mine, Silver City district, consists of a comb of quartz crystals 

 bearing loosely attached large grains of pyrargyrite and some small 

 white grains, most of which are irregular, although some appear 

 cubic. These seem later in age than the pyrargyrite. This white 

 mineral was examined optically by A. Rodolfo Martinez, who found 

 it to be isotropic with a refractive index of 1.434. It is thus shown 

 to be fluorite. 



A specimen from a tunnel on the south side of Long Gulch below 

 the Blaine tunnel, Silver City district, shows octahedral crystals of 

 pale lavender fluorite up to 3 mm. in diameter resting upon adularia 

 crystals. 



LAWRENCITE (178) 

 Ferrous chloride, FeCl 2 . 



Lawrencite or ferrous iron chloride is a soft green to brownish- 

 green substance which is known to occur only in meteoric iron. It 

 exudes from freshly cut or broken surfaces of meteorites and oxidizes 

 almost immediately to brown rust. This compound was abundantly 

 present in the meteoric iron which was found in a gold placer on 

 Hayden Creek, Lemhi County. 69 



68 J. B. Umpleby and D. C. Livingston. Idaho Bur. Mines and Qeol. Bull. 3, p. 15, 1920. 

 »» William Earl Hidden. Amer. Journ. Sci., vol. 9, p. 367, 1900. 



