52 BULLETIN 131, UNITED STATES NATIONAL MUSEUM 



A third group of gold lodes of various types occurs in Lemhi 

 County near the Montana line, while a fourth small but formerly 

 productive area is in the Coeur d' Alene district in Shoshone County, 

 where the gold occurred in banded quartz veins cutting black 

 Algonkian slates. 



The precious metal districts in Owyhee County contain both gold 

 and silver in veins mainly contained in Tertiary volcanic rocks. 

 Similar to these are the deposits of the Thunder Mountain district in 

 Idaho County, the Forney (Gravel Range) and Parker Mountain dis- 

 tricts in Lemhi County, and the Yankee Fork district in Custer County. 

 Many of the veins of this group are characterized by crustified 

 quartz, pseudomorphous quartz, or chalcedony, with or without 

 adularia, as gangue. The ores of a number of the mines contain 

 bands of finely divided silver sulphide carrying some selenium. 

 The native gold of these later Tertiary deposits is mostly pale in 

 color and high in silver content, much of it being classifiable as 

 electrum. 



Tellurides of gold are of very limited occurrence in the State, 

 practically all of the gold being in native form. Of the rarer minerals 

 accompanying the gold, bismuth sulphide (bismuthinite) and lead- 

 bismuth sulphide (galenobismutite) have been mentioned. Scheel- 

 ite accompanies the gold in the Charity vein in the Warren district 

 and in several mines in the Coeur d' Alene district. 



While no district or mine has attained a reputation for furnishing 

 remarkably showy, beautiful, or well-crystallized specimens of 

 native gold, a majority of the auriferous mines of the State have, 

 at some time during their history, produced ore of such a grade as 

 to make excellent cabinet material. Very few such specimens have 

 been preserved. Descriptions of those in the National Museum 

 collections are given below. 



Placer gold was the first form to be mined in the State and the 

 total production of it greatly overshadows that of gold derived 

 from lode mining. Dana, writing in 1890, says of Idaho u Every 

 county in the State yields placer gold." Roughly the great placer 

 regions are the same as those which have been mentioned as the 

 principal groups of lode mining districts, the greatest area being 

 that known as the Boise Basin. Gold occurs in placers in almost 

 every district where auriferous lodes are known, usually in amount 

 out of proportion to the value of the developed veins. Moreover some 

 placer districts of importance have been worked in areas where no 

 productive lodes are known. Such observations as this have given 

 rise, in Idaho as elsewhere, to the fable of the Mother Lode. A 

 sufficient source may be found, however, in the concentration from 

 the disintegration and erosion of quantities of rock measurable in 

 cubic miles including great vertical sections of the known veins, of 



