Bulletin 259 DEPARTMENT OF COMMERCE HERBERT HOOVER, SECRETARY BUREAU OF MINES SCOTT TURNER, DIRECTOR PLACER-MINING METHODS AND COSTS IN ALASKA BY NORMAN L. WIMMLER PRICE 55 CENTS SoldonlybytheSuperintendentofDocuments, Guvernment PrintingOffice Washington,D. C. UNITED STATES GOVERNMENT PRINTING OFFICE WASHINGTON 1927 CONTENTS Page Page Introduction___________________ 1 Prospecting-Continued. Reports of Geological Survey___ 1 Prospectdrilling______________ 37 Scope of bulletin______________ 2 Spacing and measurement of Acknowledgments____________ 3 holes____________________ 37 History________________________ 3 Types of drills used_________ 38 Discovery of gold fields________ 3 Steamdrills______________ 38 Production___________________ 4 Churn drill 39 Future of Alaska placer mining___ 7 Contract drilling__________ 39 Value of reserves_____________ 7 Gasoline drills____________ 40 Mining methods______________ 8 Water supply__________________ 40 Mining by hand____________ 8 Methods of measuring flow of Mechanical mining__________ 8 water___________________ 41 Hydraulic mining___________ 9 Miner's inch 41 Dredging__________________ 9 Sluice head________________ 42 Conditions affecting placer min- Determinationof flow in open ing________________________ 9 channels ________________ 42 Natural conditions 10 Alaska water conduits_________ 43 Geography_____________ _ 10 Dams and reservoirs__________ 45 Topography__________________ 10 Dams_____________________ 45 Geological features____________ 11 Reservoirs_________________ 46 Classification of placers ___ 11 Snow fences________________ 47 Creek placers____________ 11 DUches______________________ 47 Bench placers__________ _ 12 Methods of construction and Sea-beach placers_________ 13 conditions encountered__ 47 River-bar, gravel-plain, and Ditches on Seward Penin otherplacers___________ 13 sula___________________ 48 Minerals associated with Exposure and grade_______ 50 placer gold______________ 14 Maintenance and repair of Climate_____________________ 14 ditches 50 Costs_________________________ 18 Cost of construction and Transportation and freight maintenance of ditches____ 52 rates____________________ 18 Typical large ditches________ 53 Ocean, rail, and river trans- Miocene ditch____________ 53 portation 18 Fairhaven ditch__________ 53 Roads and trails____________ 24 Othertypical ditches______ 54 Possibilities of airplane serv Proposed ditch in Fairbanks ice______________________ 25 district__________________ 55 Comparison of costsby differ- Flumes and siphons___________ 56 ent methods offreighting__ 25 Successfulflumeconstruction_ 56 Labor_______________________ 26 Siphons 58 Supplies________________ ____ 28 Pipe lines, giants, and nozzles__ 58 Lumberand wood fueL_____ 28 Pipe lines__________________ 58 CoaL_____________________ 30 Laying pipe lines_________ 60 Oilfuels 31 Canvas hose_______________ 61 Prospecting____________________ 31 Hydraulic giants_____________ 61 Purnping 62 Reviewofprospectingmethods_ 32 Shafts and drifts______________ 34 Waste ditches and drains______ 62 Cost of sinking shafts and Frozen ground - 63 drill holes________________ 35 Composition of frozen ground__ 63 q6 Prospect drifts_____________ Properties of frozen ground____ 64 HI IV Page Page Preliminary work~______________ 65 Mining methods-Continued. Stripping overburden__________ 65 Open-cut mining-Continuec1 Limiting factors____________ 66 Mechanical methuds-Cont,l. Handling stripped overbur- Drag-line excavators 109 den 66 Drag-line excavator on Stripping methods__________ 66 Willow CreeL 109 Strippingon Candle CreeL 68 Drag-line excavator on Stripping on Goldstream NOrne and Caribou Creek_________________ 68 Creeks 112 Strippingon Willow Creek_ 69 Driftmining_________________ 113 Stripping on Eagle and Types of drift mines_________ 114 Mammoth Creeks______ 69 Equipment for drift mines 114 Strippingin the Klondike__ 70 Methods of development 115 Thawingfrozen graveL________ 71 Development by shafts 115 Heat required to thaw frozen Drifting_________________ 117 gravels_ _________ 71 Modified longwall method_ 119 Thawing with hot rocks and Miningfrom adits 120 wood fires________________ 72 Removal of graveL 121 Thawing by natural means or Bucket hoisL______________ 122 exposure to the elements___ 73 Sluicing 123 Steam thawing_____________ 74 Costof sluicing 125 Description of steam-thaw- Thawing___________________ 125 ing outfiL 75 Steam points_____________ 125 Spacingof points_________ 75 Setting points____________ 126 Cost of steam thawing_____ 76 Time needed for thawing__ 127 Thawing with hot water_____ 77 Costs____________________ 127 Thawingwithwateratnatural Driving points under diffi- temperatures_____ ___ 77 cult conditions 128 Miles method____________ 77 Thawingon LittleEldorado Work in Iditarod districL_ 82 Creek 128 Cost of thawing with water New drift-mining method of atnaturaltemperatures__ 85 Idaho Mining Co 129 Pierce method 85 System ofmining_________ 130 Mining methods________________ 87 Delays 131 Open-cut mining______________ 87 Safety measures and haul- Manual methods_____________ 88 age 131 Beach mining____________ 88 Reasons for success of Ground sluicing___________ 89 method 131 Booming_________________ 90 Hydraulicking 132 Shoveling in______________ 91 Primitive drift-mining meth- Costs of ground sluicing ods 133 and booming___________ 92 Costs 133 Self-dumping carriers______ 93 Hydraulic mining 134 Mechanical methods________ 94 Water supply______________ 135 Steam scrapers___________ 94 Stream grades 135 Bagley or bottomless type Ground sluice or by-wash__ 136 scrapers_______________ 95 Slip scrapers 102 Conditions governing water supply 136 Cableway excavators 105 Description of typical Capital invested in hydraulic operations 137 cableway system_____ 106 Examples of cableway Importance of hydraulic min- ing 137 operation 107 CONTENTS v Page Page Mining methods-Continued. MiIliIl~methods-Continued. Hydraulic mining-Continued. Hydraulic mining-Continued. Duty of wateL 138 Hydraulic elevators-Continued. Definition_______________ 138 Hydraulic elevator mining Data on duty of miner's on Inmachuck River____ 172 inch 138 Hydraulic elevator mining Reasons for low duty 140 on Osborne CreeL_____ 172 Hydraulicminingmethodsfor Hydraulic elevator mining benchandcreekdeposits___ 141 on Ophir Creek 173 General hydraulic mining Hydraulic elevator mining methods 142 in Iditarod district____ 174 Piping into the head of the Rubble elevators 174 boxes 142 Operating data___________ 175 Sluice boxes 143 Dredging 176 Placer on Falls Creek___ 144 HistoryofdredginginAlaska_ 176 Hydraulic mine at Crow Future of dredging 176 Creek 145 Factors determining dredg- Piping over side of sluice ing . 177 boxes when boxes are Data on dredges 178 setinbedrockwithtops Types of dredges___________ 178 below surface 146 Flume or single-Hluice Hydraulicminingon Dan dredge 179 Creek 147 Flume-type dredge with Hydraulic mmmg on revolving screen 183 Chititu Creek 150 Combination-type dredge__ 184 Discussion of method 152 StaCker-type dredge 186 Piping over side with lower Details of dredge construc- sluice boxes set in or tion 188 on bedrock and upper Hulls 188 ones on or above bed- Bucket lines 188 rock surface 153 Effect of digging conditions__ 190 Placer on Eagle Creek 153 Length of dredging season___ 190 Ice 191 PlaceronCrookedCreeL 156 Pipingoversidewhenboxes Heat and lighL 192 are on or above bedrock_ 158 Operating data_____________ 192 Combination of piping over VVages 19~ side and into head of Power costs______________ 194 boxes 159 Cache Creek dredge 195 Placer on Mastodon Dredging at Nome 196 Creek 159 Methods of estimating yard- Disposal of bowlders 161 age dredged 196 Disposal of tailing__________ 164 Gold content of ground Hydraulic mining costs______ 166 dredged 197 Costs of typical mining projects_______________ 166 Dredge operating costs______ 197 Hydraulic elevators_________ 167 Detailed data from indi Principle of operation_____ 167 vidual operations_______ 198 Arrangement of equipment- 168 Typical placer in interior Elevator mining on Little district________________ 202 Creek, near Nome 170 Cost of gold dredges________ 203 Equipment- 171 Specimen costs___________ 204 Cost and production______ 171 Movement of dredges 204 VI CONTENTS. Page Page Gold saving 205 Gold saving-Continued. Clean-up 214 Gold saving in mining methods other than dredging_______ 206 Sluice boxes i 214 Sluices 206 Dredges 215 Sluice drops 207 Recovery of gold and preparation Mud or dump boxes 207 for market 215 Riffies_____________________ 208 Cleaninggold dustoramalgam_ 215 Cleaning heavy sands 216 Poleandwood-block riffies_ 208 Use of cyanide 217 Steel-rail, angle-iron, and Retorting amalgam 217 cast-iron riffies_________ 209 Precautions________________ 217 Steel plates 210 Melting retort sponge into bul- Rock or cobble riffies 210 lion 218 Undercurrents and gold Assayingand shipmentofplacer tables 210 gold 218 Gold saving in dredging_______ 211 Alaska placer-mining law and tax- Riffies 212 ation 220 Undercurrents 212 Placer-mining law____________ 220 Screens 212 Duties ofmine inspectors______ 222 Save-aIls and other appli- Taxation____________________ 223 ances 213 Selected bibliography 225 Mercury 213 Index 229 ILLrSTRATIOXS ~ ~~ 1. ~Iap of Alaska, showing Rituation of mining diRtricts_______________ 4 2. ProRpecting by drilling; 0111 Brow~r drill near Nome_______________ 39 3. Drilling shallow ground with 4-iu~h drill driven by gasoline engine__ 40 4. Typical small dam, made of brush, gravel, and sod, for diverting water to ditch________________________________________________ 45 5. Dam and flume on Dan Creek. Xizina distri~L____________________ 46 6. Settling pond for tailing. Iditarod distl'jeL________________________ 41 7. Hemainillg portion of snoW bridge over Miocene ditch, July 5, 1922__ 51 8. Flume ill the Rampart distril'L__________________________________ 57 9. Dam, penstock, aud head of pipe line, Kizina district______________ 59 10. Ground sluicing muck overbul'den________________________________ 67 11. Hydraulic stripping of overburden ahead of dredging_______________ 67 12. Bagley scraper operation on Goldstream Creek, FairbankR distrieL__ 69 13. Driving steam-thawing points ahead of dredge______________________ 74 14. Water thawing ahead of dredges at Nome________________________ 79 Hi. Driving water-thawing points with anv:! attachment, at Nome____ 81 16. Thawing with water on Otter Creek, Iditarod distrieL_____________ 83 17. Beach mining with long tom at Nome____________________________ 88 18. Beach mining with surf waRherR at Nome_________________________ 89 19. Shoveling into boxes below automatic dam, Rampart districL_______ 90 20. Automatic gate, box type, Rampart lliRtrieL______________________ 91 21. Typical Bagley scraping and loading operation____________________ 97 22. Bagley scraper delivering load to underground Rtation and car taking load from underground station to the sluice____________________ nR 23. Bagley Rcraper operation; car delivering to f'luice________________ n9 24. Sluice showing block riffles and f'pecial liners; alf'o hangers for backstop as used for hydraulicking --__--______________ 101 25. Typical f'lip-Rcraper arrangemenL_________________________________ 102 26. Slip-f'craper operation; Rcraper has jnst hN'n 10aded________________ 103 CONTENTS vn ~~ h~ 27. Slip ~erapel' traveling up illdille to Hluiee~_________________________ 103 28. Cableway exeavator dumping into sluiees__________________________ 105 29. S1{eteh of cableway excavator mining______________________________ 106 30. C~bleway excavator plallt_________________________________________ 107 31. Drag-line excavator bucket loading_______________________________ 110 32. Locally constructed drag-line excavator, Nome Creek, Fairbanks dis- trict___________________________________________________________ 112 83. Section of a drift mine____________________________________________ 118 34. Underground and surface arrangement of drift mine_______________ 119 35. Fairbanks self-dumping bucket and carrier_________________________ 122 36. Surface arrangement of drift mine in interior of Alaska____________ 123 37. Sluicing the dump by nozzling_____________________________________ 124 38. Hydraulic mining. Piping into the head; sluice-box extension______ 143 39. Hydraulic mining in Yentna district. Piping into the head_________ 144 40. Hydraulic mining at Crow Creek. Wings and sluices_______________ 145 41. Plan showing method of piping over the side of boxes, advancing downstrealn____________________________________________________ 148 42. Hydraulic mining on Dan Creek. Completed pit showing bedrock sluice and removal of the boxes________________________________ 149 43. Removing and cleaning up the sluices, Dan Creek .__ 149 44. Piping over the Ride on Chititu Creek______________________________ 151 45. Method of piping over the side, advancing upstream________________ 151 46. Method ofpiping over the side as uRed on FJagleCreek,CircledistricL 154 47. Combination method of hydraulic mining (circle system) as used on Mastodon Creek 160 48. Difficult hydraulic mining in Iditarod district. Derrick for handling bowlders_______________________________________________________ 162 49. Bowlder disposal. Loading the steel stone boaL__________________ 162 flO. Drilling a bowlder before blasting it, Crow Creek________________ 163 51. Stacking tailing with the gianL___________________________________ 165 52. Installing hydraulic elevator and sluice boxes near Nome________ 169 53. Opening elevator pit, driving to elevator___________________________ 170 54. Elevator and sluices______________________________________________ 172 GG. Rubble elevator on Candle Creek, Fairhaven districL_______________ 175 :'6. A l14-cubic foot flume dredge. formerly on 'Varm Creek____________ 179 57. The2~-cubicfoot distillate-driven flume dredge on Yankee Creek____ 179 58. Plan of 2~-cubic foot distillate-driven flume dredge with under- current________________________________________________________ 182 G9. Electrically driven61h-cubicfoot screen-flume dredge on Cache Creek_ 183 60. Flume of the Cache Creek dredge________________________________ 183 61. Steam-driven combination-type dredge on Mammoth Creek________ 184 tl2. Plan and elevation of 3th-cubic foot combination-type dredge with revolving screen, flume, and conveyer and with undercurrenL______ 185 63. Conveyer and two flumes on the Berry dredge______________________ 186 64. The 31f2-cubic foot Remi-Diesel-driven sta<'ker dredge on Candle Creek in the Kuskokwim________________________________________ 186 65. No. 1 dredge of Hammon Consolidated Goldfields Co., at Nome; a 9-cubic foot electrically driven stacker (h·edge____________________ 187 66. A light 21h-cubic foot open-connected hueket line on flume dredge__ 188 67. A. 61;2-cubic foot close-eonneded hucket lilw of special design______ 189 68. Steam ice<'utter__________________________________________________ 191 69. Dump or mud box-_______________________________________________ 207 70. Sluice-box undercurrenL ---- =--"""- 210 PLACER-MINING METHODS AND COSTS IN ALASKA By NOltl\L\N L. ",V1l\IMUm INTRODUCTION Active placer mining in Alaska began near Juneau in 1880, but the first gold rush did not start until 1896; then the discovery of the Klondike brought gold seekers from all parts of the world. A few of the newcomers were experienced miners, but the majority knew nothing whatever of placer mining. Even those who were placer miners of much experience found entirely new conditions, notably frozen ground, that presented many difficult problems. As a result, numerous methods of mining and of thawing frozen ground were tried. From these trials the practice described in this bulletin has been developed. . All known placer fields in Alaska have been mined to some extent, and some have been virtually exhausted. In most districts, however, there remainlargequantities oflow-grade gravel and also some small isolated areas of comparatively rich gravels which could not be suecessfully mined because of adverse physical conditions. These district~ are now the scene of most placer mining, including dredg ing, hydraulicking, drifting, mechanical methods of open-cut min ing~ and ground sluicing (or booming) followed by " shoveling-in." As the richer areas were exhausted, fewer mines were worked and production declined. The increased cost of supplies incident to the World War depressed mining further. Economic conditions are now much better, the cost of equipment and supplies is lower than for years, and transportation to the more important districts, especially those reached by the Alaska Railroad and its river steam ers, has improved. Methods of thawing frozen gravel with water at natural temperature have been developed, and the efficiency of mechanical equipment and power generation has been advanced. :Mining costs have been reduced thereby and an impetus given to placer mining. REPORTS OF GEOLOGICAL SURVEY The published reports of the United States Geological Survey, which cover more than 30 years' work in Alaska and include geo logical studies, water-supply papers, investigations of placer mining: 1 2 PLACER-MINING METHODS AND COSTS IN ALASKA and the annual reports on the Alaska mining industry, haye been invaluable. Most of this work was directed by the late Dr. AUred H. Brooks, who, as chief geologist of the Alaska division for 25 years, probably did more than any other person to aid mining in Alaska. In 1904, ,vhen Alaska placer mining was nearing its peak of production, the late C. 'V. Purington investigated methods and costs of gravel and placer mining; his excellent report thereon has 1 been accepted as authoritative for Alaska practice. -Meanwhile, many other placer districts have been discovered and actively mined, mining practice has been modifietl and improved,andeconomiccondi tions have changed. SCOPE OF BULLETIN This bulletin gives the results of a study of present conditions in Alaska placer mining, including the methods employed and the costs, and will be helpful to placer miners, engineers, and all others interested in the industry. Gold placers are widespread in Alaska. There are more than 50 known mining centers, the relative locations of which are indi cated onthe map (fig. 1). The writer could examine only the typical districts, beginning his field work at :Kome in June, 1922, and later visiting the Solomon, Council, and Bluff districts on Seward Pen insula, then the Ruby, Hot Springs, Rampart, and Fairbanks districts. In 1923 he examined the Iditarod, Innoko, a part of the Kuskokwim, the Fairbanks, Yentna, Nizina, and Girdwood dis tricts. In August, 1924, he made an airplane flight of 220 miles from Fairbanks to Eagle amI visited part of the Fortymile district, the Eagle, Seventymile, and Circle districts, and later the Fair banks and Girdwood districts. John A. Davis, of the Bureau of ~1:inesstaff, visited the I(oyuk, Candle, Inmachuck, Nome, Solomon, and Council districts on the Seward Peninsula during 1924 to obtain further data for this bulletin. Although operators willingly supplied available data on operating practice and costs, only in formation that was deemed pertinent has been used. To check figures as to the area or yardage mined, the average amount of water used, and similar details has been practically impossible, but the figures given are the best obtainable. The investigator did not attempt to sample deposits, ascertain the extent of gold-placer re serves, determine the water resources, or study similar features in detail. Valuable material on some districts which could not be visited was obtained by conferences or correspondence with operators and other responsible persons. Government publications and many 1Purington. C. W" Methods and Co~t~ of Gmvt'l and PhH'pr Millill~ in .\la~ka: U. S. Geol. Survey Rull. 26:{, 190;), 273 pp.