GEM MINING IN THE UNITED STATES 



67 



providcil with the tourmalines. On opening 

 the rock the veins are found to be widely 

 and variously altered by decomposition, re- 

 sulting from the infiltration of water, with 

 the inevitable change of the feldspar into a 

 soft discolored clay. The tourmalines are 

 uncoveretl in pockets — usually detached — 

 lying on the clay beneath them. Secondary 

 crystallization has ensued through these in- 

 terior changes, and in the so-called "live 

 pockets" (a not unreasonable designation 

 when one sees the activity their presence 

 entails among the workers) the quartz crys- 

 tals are themselves coated with a thin crust 

 of tiny tourmalines, which are absent in the 

 "dead pockets." 



At Mt. Apatite, some four miles from the 

 town of Auburn, similar, but differently 

 conditioned, relations occur. The Pulsifer 

 and Keith Mine on the southwest side of the 

 mountain has been worked for gems in a 

 small way for forty years, and in 1907 — as 

 Mr. Pulsifer informs me — it was first worked 

 for feldspar, in conjunction with the unin- 

 termittent search for the gems. Here the 

 signs which indicate the neighborhood of the 

 gem matter are a lamellar form of the feld- 

 spar, albite (cleavelandite) and the lithia 

 mica, embedded in the coarse granite. In 

 June, 1916, Mr. Pulsifer secured at one 

 point, six thousand carats of blue-green tour- 

 maline, and encountered in the vicinity sev- 

 eral pockets of the mineral herderite, a 

 beryllium salt, and justly eminent as a niin- 

 eralogical prize. 



A further survey of tourmaline mining in 

 the United States transports us to southern 

 California — a region where tourmalines, 

 kunzite, and the many lithia compounds, 

 flashed their hues and displayed their mas- 

 sive development, not so many years ago, to 

 an amazed and almost incredulous world, 

 repeating, as everyone soon discovered, the 

 mineral phenomena of central Madagascar. 

 The region in California which, some twenty 

 or more years ago, began to jdeld to ex- 

 plorers these uncommon crystals, lies almost 

 wholly in San Diego County. The localities 

 of Pala, Pala Chief, Mesa Grande, and Ra- 

 mona practically furnished the largest part 

 of the commercial output of tourmaline, a 

 gem finding one of its best markets in China, 

 whose merchants exult in its richness of 

 color and its impressiveness of size. 



In San Diego County there may be seen a 

 series of moderately high mountain ridges, 



culminating in elevations of over five thou- 

 sand feet, which overlook the plainlike ex- 

 panses at their feet. These inauspicious 

 elevations are the lit hie pediments of large 

 igneous outflows, and have themselves under- 

 gone, under the repeated invasions of later 

 lava-like masses (now recorded in the trav- 

 ersing granite veins), extensive metamorphic 

 alterations. Throughout the invading mag- 

 mas of granitic lavas the processes of miner- 

 alization have generated the extraordinary 

 gem contents of the decomposed hosts, as- 

 sisted by intensely active chemical agencies, 

 in the boron, hot silica baths, and varying 

 proportions of lithia-bearing waters. 



Here, in pockets, in seams, and in druses, 

 a most remarkable retinue of minerals has 

 been crystallized, in some cases showing a 

 rude stratified segregation, the whole tran- 

 spiring probably, in long continued and suc- 

 cessively reinforced periods of digestion and 

 change. Here the gem stones, tourmaline and 

 kunzite have formed, the commercially valu- 

 able lithia-eontaining lepidolite, and am- 

 blygonite, with a clustering association of 

 many-colored quartzes, potash and soda feld- 

 spars, beryls, garnet, epidote, and micas 

 with later derivatives, and were perhaps pre- 

 ceded by original emanations of sulphides 

 and native metallic sublimates. 



A mineral individuality is discoverable in 

 these marvelous belts of mineral profusion, 

 so that the lithia mica with its splashes of 

 radiating red tourmaline, and with am- 

 blygonite, prevails in one region, the big 

 diversely colored tourmalines in another, 

 kunzite, in the loveliest shades of gentian 

 and lilac, in still a third, and garnet and 

 topaz in a fourth. Scant justice can be done 

 in words to this prodigality, and while the 

 collectors revel in the abundance of color 

 and species, the crystallographer is no less 

 astonished at the local peculiarities of for- 

 mal development in the crystals. 



The tourmalines and kunzites have, of 

 course, given the region its fame as a gem- 

 producing locality, and the size and color of 

 the former have momentarily eclipsed the 

 (daims of all other localities. In the Morgan 

 Gem Collection in the American Museum of 

 Natural History are to be seen the cut 

 rubellite — beautifully zoned gems, with red 

 at one end of the polished cabochon and 

 green at the other, while in a wall case are 

 grouped the colossal crystals of rubellite, 

 inserted in the sides of vellow-white crystal- 



