COLLECTIONS IN ECONOMIC OEOl.OGV AND METALLURGY. 9 



(7) Pyrite, uutliTgoiiii; (lec()mi)()Hit.i(>ii, and ■stiiiniii,'; «iii;irt/.. Ellin Mine, Ciilpt'.pcr 

 County, Virginia. (3375;").) 



(8) Crystallized pyrite, almost wholly altered to the hydrated oxide of iron, with 

 a little quartz. Narcoochee Mine, White County, Georgia, ((iolol.) 



(9) Mispickel, (snlpharseuide of iron), crystallized in dolomite and quartz. Lake 

 Mountain Mine, Sitka mining district, Alaska. (5056.) 



(10) Mispickel, (aulpharsenide of iron) with quartz. PLaley & Milstick Mine, near 

 Silver Bay, Baranofi' Maud, Alaska. (34413.) 



TELLURIDE ORES. 



These ores consist of various telluridesofgokland silver, toi^ether with 

 free gold and free tellurium in a gangue of quartz, occurring for the most 

 part ill veins, and associated with other ores. They are of limited occur- 

 rence, except in the case of a few Colorado mines, which at one time 

 produced large amounts. Tlie process of extracting the gold varies 

 according to circumstances, the most simple being to roast the ore, 

 whereby the tellurium is driven off, and the gold set free, and then to 

 crush and amalgamate. Much of this kind of ore is treated by fusion 

 processes. 



To illustrate the telluride ores five specimens are shown : 



(1) Tellurides in porphyry. Superior Mine, Sugar Loaf district, Boulder County, 

 Colorado. (19273.) 



(2) Roasted telluride ore, showing metallic gold set free hythe roasting. Superior 

 Mine, Sugar Loaf district, Boulder County, Colorado. (19270.) 



(3) Tellurides, with a little pyrite in quartz. Cold Spring Mine, Gold flill district, 

 Boulder County, Colorado. (19072.) 



(4) Tellurides and free tellurium, crystallized, with a little pyrite in quartz. Key- 

 stone Mine, Gold Hill district, Boulder County, Colorado. (19137.) 



(5) Tellurides and free gold, with pyrite in quartz. Ameiican Mine, Sunshine dis- 

 trict, Boulder County, Colorado. (19090.) 



FUSION GOLD ORES. 



These ores are generally ores of other metals besides gold, and the 

 gold is separated during the process of separating the other metals. 

 They may be broadly separated into auriferous copper ores, auriferous 

 silver and lead ores, and a third class containing very variable ores. 

 To this latter class belong many of the telluride ores. Xo especial col- 

 lection of fusion ores is shown, but they can be seen in the collections 

 from the Argo Works, Colorado, and the Balbach Works, Newark, New 

 Jersey, and also as the auriferous varieties of the ores of other metals. 

 In the latter case no especial distinction can be seen between the aurif- 

 erous and uon-auriferous varieties of the ores of other metals. 



Processes of Extracting Gold. 



hydraulic gravel deposits. 



Along the slopes of the Sierra Nevada Mountains of California occur 

 immense bodies of gravel, made up of a large variety of material, and 

 while quartzose sand and pebbles i)redominate, yet other materials are 



