GEM MINING IN THE CM TED STATES 



69 



ship among Americau gem industries. It 

 appears to be a product of alteration, and is 

 invariably symptomatic of igneous intru- 

 sions, with consequent decomposition, fol- 

 lowed in many fields by a later saturation of 

 the corroded rocks by quartz. This last in- 

 vasion has cemented the whole complex into 

 rugged refractory strata. The turquoise, 

 exhibiting the widest range of quality, oc- 

 curs as nuggets and balls, and in veins and 

 seams with interspersed incrustations. 



The demand for this gem is not easily 

 satisfied, and the output in 1908 was ap- 

 praised at $150,000, to which yield Nevada, 

 Colorado, New Mexico, Arizona, and Cali- 

 fornia contributed. Turquoise is not re- 

 garded with unstinted admiration by the 

 gem collector; it has too often repaid his 

 confidence with disappointment by its loss 

 of color. Not admitted into the first rank 

 of gems it is classed among the second and 

 even third-class stones, because of this ten- 

 dency to deterioration. But in its most 

 perfect state the soft blue of the turquoise, 

 rendered precious in fine examples by its 

 durability, rivals the other gems. At any 

 rate it has been cherished by connoisseurs 

 for many centuries, and its popularity today 

 is unmistakable. Dr. Berthold Laufer of 

 the Field Museum, Chicago, says that in the 

 eyes of the Tibetans the turquoise had a 

 sacred character that lifted it above the 

 ordinary category of stones; "to call a 

 turquoise a stone, to the Tibetan, is offen- 

 sive, and his indignant remonstrance DI YA 

 BE, DO MA BE, informs the astonished 

 visitor that it is a turquoise and not a 

 stone." 



Mohave County in Arizona has monopo- 

 lized the turquoise product of the state. 

 One approaches a group of hills which are 

 the more or less isolated elevations distin- 

 guishing the west side of the Cerbat Eange 

 and included in the general geographic 

 designation of ^Mineral Park. The litholog- 

 ical conditions embrace a preexistent Pre- 

 Cambrian rock, invaded t»y later granites 

 and poi-phyries. The gem stones are found 

 in these intrusions, which, weathered and 

 eroded, assume a high relief, the rigidity of 

 outline being maintained by saturation of 

 the mass by quartz. 



Processes of alteration succeeding one 

 another in more or less defined order, have 

 been accompanied by circulating solutions 

 depositing or fonning turquoise. Dark 

 stains of iron oxide blotch the seams of 

 quartz or turquoise, and the variegation of 

 color is heightened by copper stains of blue 

 and green smearing the kaolin with vivid or 

 dull, faded streaks, like the droppings from 

 a paint brush. The turquoise is found ir- 

 regularly developed in veinlets of rock 

 crevices, with rarely a tendency to form a 

 nuggety mixture, from which sizeable gems 

 may be extracted. 



In almost all the workings, here and else- 

 where, the turquoise is a secondary occur- 

 rence, consequent upon the initial decom- 

 position of the matrix, and the later 

 entrance into the jointed mass of phosphate 

 solutions, with the final "setting" of the 

 gem itself in favorable nuclei of concen- 

 tration and along narrow ribbons of inter- 

 stitial quartz. In some workings veins six 

 to eight inches in thickness are encountered, 

 while elsewhere the turquoise penetrates its 

 host in threads, or appears in patches, 

 rather haphazardly yielding pure turquoise, 

 semi-turquoise, and green soft kaolin. The 

 finest quality of stone is not common, and 

 the sorting — which is very exhaustively done 

 — separates out the greenish pale varieties 

 and the soft turquoise, both of which are 

 worthless for commercial purposes. 



A picturesque situation has been devel- 

 oped by the Arizona Turquoise Coiupany. 

 This company has attacked the steep slope 

 of Ithica Peak, one of the Mineral Park 

 sumniits, and entered the mountain-side by 

 an open cut. The operation involves the 

 formation of a series of terraces, each twelve 

 to fifteen feet high. Drill holes are sunk 

 and great masses of rock dislodged by blast- 

 ing. Hundreds of tons of rock are thus 

 brought under the sledge, and from the 

 broken and crushed fragments the turquoise 

 is picked out. There is an eager scrutiny 

 for the fine-colored stones, which are after- 

 ward more tenderly extracted with smaller 

 implements, and some solicitude. The stim- 

 ulated interest in turquoise urgently requires 

 for its satisfaction new developments of the 

 pure blue anil permanent mineral. 



