Februaey 12, 1904.] 



SCIENCE. 



267 



San Jacinto Mountains. The places where 

 working mines are located are not many and 

 may be grouped under four heads — those at 

 (1) Pala, (2) Mesa Grande and (3) Oak 

 Grove in San Diego County, and those at 

 (4) Cuahuila in Riverside County. 



1. The mines at Pala consist of the famous 

 lepidolite mine from which the well-known 

 specimens of rubellite come and the spodu- 

 mene mine, about a mile away, which has 

 already been described by the writer. The 

 immense deposits of lithia minerals at the 

 lepidolite mine occur in a pegmatite dike 

 striking across a large body of diorite and 

 dipping towards the west at a low angle. This 

 dike is about a mile long and has a thickness 

 of from twenty to eighty feet. 



The pegmatite, in which large bodies of 

 lepidolite and other lithia minerals occur, con- 

 sists of a coarse muscovite-granite with gar- 

 nets and black tourmalines. There are at 

 least four of these large bodies of lepidolite 

 exposed, only one of which is at present being 

 mined. A conservative estimate of the size 

 of this body of lepidolite, now in sight, would 

 be 200 X 100 X 25 feet. In some parts radi- 

 ated groups of rubellite occur, and near the 

 northern end of the body quartz and feldspar 

 become rather abundant and the deposit seems 

 to grade into the normal muscovite-pegmatite. 



The pink clay — so often associated with 

 gem tourmalines — occurring here has been de- 

 termined to be halloysite. A large deposit of 

 pure amblygonite, showing broad cleavage 

 faces, has been uncovered. Numerous well- 

 terminated green tourmalines, with complex 

 combinations, have also been found, as well as 

 several pounds of native bismuth and its 

 oxidation products, bismuthinite and bismuto- 

 sphserite. The bismutosphserite occurs in 

 grayish-black masses and also as a yellow 

 powder. A qualitative test showed the pres- 

 ence of carbonic acid and the absence of 

 water. Doubly terminated quartz crystals are 

 not uncommon. The list of minerals from 

 this mine so far identified is lepidolite, tour- 

 maline (black, green, pink), amblygonite, 

 orthoclase, muscovite, quartz, kaolinite, hal- 

 loysite, garnet, plagioclase feldspar, bismuth, 

 bismuthinite and bismutosph^rite. 



At the spodumene mine the following min- 

 erals have been identified: tourmaline (black, 

 pink, blue, blue-green), spodumene, lepidolite, 

 beryl (pink), quartz, muscovite and orthoclase. 



Very pale green, colorless and lilac-colored 

 spodumene has been found in the mountains 

 a few miles east of the mine. 



2. The Mesa Grande district is the most im- 

 portant one for tourmalines. Two mines, only 

 one of which was accessible to the writer, are 

 situated here, both being located on the same 

 series of pegmatite dikes. The country rock 

 in which these muscovite-granite dikes occur 

 is a diorite. 



In the mine visited three such dikes are 

 being followed, only one of which is at all rich 

 in tourmalines. The dikes, only a few feet in 

 thickness, dip southwest at an angle of 45° 

 and are usually not much decomposed. Some- 

 times, however, the granite has become altered 

 to a red clay and then this is carefully searched 

 for loose tourmalines. Lepidolite is not abun- 

 dant and is usually rather coarse. Muscovite, 

 with a lepidolite border, is of frequent occur- 

 rence. Several fine crystals of lepidolite have 

 been found in this mine, one complete crystal 

 measuring 10 mm. across the base and having 

 a height of 6 mm. 



The tourmalines are mostly pale pink, 

 though some red ones of good color, as well 

 as green ones, have been found. Several good 

 achroites have also been found, one in the 

 possession of the writer measuring 35' mm. 

 in length and 14 mm. in thickness. Besides 

 the minerals mentioned above, quartz and 

 orthoclase in large, complete crystals are found 

 here. Garnet and beryl occur in the inrme- 

 diate vicinity. 



3. The geology of the Oak Grove mine is 

 similar to that of the other localities. Some 

 of the cut tourmalines from this mine are 

 exceedingly brilliant. Several fine yellow 

 tourmalines have been obtained here. The 

 minerals occurring at this mine are the same 

 as those found at the Mesa Grande mine. 



4. The Cuahuila locality is similar to the 

 others, and the list of minerals found here 

 includes tourmaline (pink, green, blue, blue- 

 green, smoky, colorless, yellow and black), 

 spodumene (the amethystine variety), beryl 



