B14 



SCIENCE 



[N.S. Vol. XXXVIII. No. 983 



tite is accordingly the largest source of 

 radium at the present time, and at least 

 four times as much radium was mined in 

 America in the form of earnotite in 1912 as 

 has been produced from Colorado pitch- 

 blende since it was first discovered in that 

 state. 



Outside of earnotite and pitchblende, the 

 only known source of radium is the mineral 

 autunite. The autunite deposits of Por- 

 tugal have probably furnished a few milli- 

 grams to commerce, and from the Mt. 

 Painter deposits in South Australia a few 

 tons of autunite-bearing ores have been 

 shipped to London. 



American earnotite is found chiefly in 

 Montrose and San Miguel counties, Colo- 

 rado, and in Utah, northwest of these 

 counties. The Utah deposits are at Green 

 River, Table Mountain, Richardson, Fruita, 

 Moab, and some sixteen miles south- 

 east of Thompsons. The ores of these de- 

 posits are of a lower grade than those of the 

 Paradox Valley, but they are nearer to the 

 railroads and transportation costs are much 

 less. The Green River deposits have appar- 

 ently become regular producers. In Colo- 

 rado, prospects have been opened at Coal 

 Creek, fourteen miles north of Meeker, and 

 at Skiill Creek, sixty-five miles west of 

 -Meeker, but the richest of all American 

 earnotite localities and, indeed, the richest 

 known radium-bearing region in the world 

 is that of the Paradox Valley, extending 

 from Hydraulic on the north to the Mc- 

 Intyre district on the south. 



Geologists are now in the field making a 

 special study of these earnotite ores with 

 special reference to their occurrence and 

 origin, of which altogether too little is now 

 known. In the Paradox region, the deposits 

 seem to lie invariably just above the fine- 

 grained La Plata sandstone. This rock is 

 usually exposed high on the sides of the 

 canyons, some of which are excelled in ex- 



tent and in natural beauty by only the 

 Grand Canyon itself. In a few instances, 

 as at Long Park and Club Ranch, the de- 

 posits are only a few feet under the sur- 

 face, the higher formations having been 

 eroded ; but for the main part, the stratum 

 in which the earnotite occurs, when not 

 entirely eroded, is deep below the surface 

 of the mass. Accordingly prospecting is 

 mainly carried on along the sides of the 

 canyons, and where vanadium and uranium 

 stains are seen upon the rock the prospector 

 blasts his tunnel in the hope of developing 

 a pocket of the ore. The fact that the ore 

 occurs in pockets renders prospecting un- 

 certain, and there appears to be no present 

 hope of insuring a successful search for 

 pockets that are not exposed, or do not 

 happen to be near the surface. Although it 

 is probable that many other pockets of ear- 

 notite occur at the same geologic horizon, 

 their discovery, except where the ore-bear- 

 ing stratum has been exposed by erosion, 

 appears at present to be an almost hopeless 

 task. The eroded sides of the canyons have 

 been prospected again and again, but new 

 claims are still being opened and are being 

 sold by the prospector to the larger com- 

 panies or operators who mine the ore. In 

 such a sale the prospector and the pur- 

 chaser both take a decided risk, for at pres- 

 ent no method is used to determine the ex- 

 tent of the ore in the pocket other than the 

 "prospector's hole." 



As few of the prospectors of the west are 

 acquainted with earnotite and pitchblende, 

 the following description of the ores has 

 been issued from the Denver office of the 

 Bureau of Mines and is sent to all who make 

 inquiry : 



In reply to your letter for information concern- 

 ing radium ores, the following facts may be of in- 

 terest : 



Radium is found with uranium minerals only. 

 Wherever uranium exists, radium is also found in 

 the mineral ; and where there is no uranium, radium 



