Mica and Beryl Pegmatites in Idaho and Montana GEOLOGICAL SURVEY PROFESSIONAL PAPER 229 Mica and Beryl Pegmatites in Idaho and Montana By W. C. STOLL GEOLOGICAL SURVEY PROFESSIONAL PAPER 229 .A descrz"ption of mines and prospects examz"ned in each district, some z"llustrated by maps .and structure sections • UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1950 UNITED STATES DEPARTMENT OF THE INTERIOR Oscar L. Chapman, Secretary GEOLOGICAL SURVEY W. E. \Vrather, Director • For sale by the Superintendent of Documents, U. S. Government Printing Office Washington 25, D. C. - Price $1.50 (paper cover) CONTENTS Pa.~re Puge Abstract--------~---------------------------------- 1 Mines and prospects in Idaho-Continued Introduction ______________________________________ _ 1 Latah County (A von mica district)-Continued Purpose of investigation ________________________ _ 1 Fitzgerald property ___________________ -_- __ _ 27 Field work and acknowledgments ________________ _ 1 Last Chance mine _________________________ _ 28 Previous work _________________________________ _ 2 Location and access ____________________ _ 28 History of mining __________________________________ _ 2 History, workings, and production _____ -·-_ 28 Geologic features and origin of pegmatites ____________ _ 3 Mica deposits _________________________ _ 28 ... Mineralogy of mica and beryL ______________________ .:. 5 Cut No. L __________ - ______ -- ____ _ 28 Mining, preparation, and uses of mica and beryL _____ :.._ 6 Cut No.2 ________________________ _ 29 Mines and prospects in Idaho _______________________ _ 8 Underground workings _____________ _ 29 Distribution of known deposits __________________ _ 8. Cut No. 3 ____________ ..: ___________ _ 29 Production and reserves ________________________ _ 8 Reserves ______________________________ _ 29 Adams County ________________________________ _ 10 Lindquist prospect _________________________ _ 30 Clarkprospects-----------------------~----- 10 Lucky Jim prospect_ _______________________ _ 31 Mica Queen mine __________________________ _ 10 Luella mine _______________________________ _ 33 Location and access ____________________ _ 10 Location, history, and production ________ _ 33 History and production ___ -.- ____________ _ 10 'Vorkings _____________________________ _ 33 VVorkings _____________________________ _ 11 Rocks and structure____________________ _ 33 Mica deposits ___________ - _____________ _ 11 Mica gneiss and schist ______________ _ 33 Boise County ______________ - _---- _______ - _____ _ 11 Pegmatites ________________________ _ 34 Mica Slim prospect ______ -: _________________ _ 11 Basalt dikes, joints, and faults _______ _ 34 Vaught columbite prospect __________________ _ 12 Economic possibilities __________________ _ 34 Bonner County ________________________________ _ 13 Maxine No.2 mine ____ _: ___________________ _ 34 Berry Creek mica prospect __________________ _ 13 McCornack property _______________________ _ 35 Soldier Creek beryl prospects ________________ _ 13 Morning Star claim ________________________ _ 35 Boundary County ____________ ------ __ --_-_- ___ _ 13 Muscovite mine ___________________________ _ 36 Lion Head prospect_ _______________________ _ 13 Location and workings _________________ _ 36 Clearwater County _____________________________ _ 14 History and production _________________ _ 37 Bobs Creek mica prospect_ _________________ _ 14 Summary of geology ___________________ _ 37 Partridge Creek mica prospect _______________ _ 15 Mica schist_ __________________________ _ 38 Idaho County _________________________________ _ 15 Alt.ered schist _________________________ _ 38 Hallmadge prospect __________________ ~ _____ _ 15 East pegmatite ________________________ _ 38 Hidden Fawn and Deer Ridge prospects ______ _ 15 Central pegmatite _____________________ _ 39 Myers mica mine __________________________ _ 16 Extent and structure _______________ _ 39 0. K. prospect _____ ._ ______________________ _ 17 Albite-quartz pegmatite ____________ _ 39 Latah County (A von mica district) ______________ _ 17 Quartz-albite-muscovite-beryl pegma- Location and accessibility ___________________ _ 17 tite ____________________ ,.. _______ _ 39 Topography _______________________________ _ 18 Border. zone _____________ -.- ________ _ 40 Geology __________________________________ _ 18 VVest pegmatite ________________________ _ 40 Pegmatites ________________________________ _ 19 Basalt ________________________________ _ 40 Mineralogy ________ - - _ -_- _____ - _ - _____ _ 19 Faults _____________________ ~ __________ _ 40 VV all-rock alteration ____________________ _ 20 Mica and beryl deposits ________________ _ 40 Structure _____________________________ _ 20 Main open pit ____________ :_ ________ _ 40 Production ________________________________ _ 21 Pit No.3 _________________________ _ 41 Conditions affecting pro-specting and mining ___ _ 22 Montag No. 1 pit __________________ _ 42 Avon Mica Co. mine _______________________ _ 22 East tunneL ______________________ _ 42 Gampbelllease _____________ - _____ ----- ____ _ 24 No. 4leveL _______________________ _ 42 Carlson lease _____________________ - ________ _ 24 SubleveL _________________________ _ 43 Doerr property and Gillis lease ______________ _ 26 Raise No. 4 _______________________ _ 43 Location and access ____________________ _ 26 No. 5leveL ______, _____________ .___ _:_ 44 History, production, and. workings _______ _ 26 Stopes No. 1 and No.2 _____________ _ 45 Rocks and structure ____________________ _ 27 Stope No. 3 __________ ~- ___________ _ 45 Mica deposits _________________________ _ 27 Stope No. 4 _______________________ _ 46 Cut No. 2 ________________________ _ 27 Old dumps ________________________ _ 46 Cut No.6 ________________________ _ 27 Reserves ______________________________ _ 46 Bureau of Mines trenches ______ ~ ____ _ 27 Reserves available ·to und~rground min- Reserves ______________________________ _ 27 ing ___ ~-------------------------- 47 III IV CONTENTS Mines and prospects in Idaho-Continued Page. Mines and prospects in Idaho-Continued Pagll· Latah County (Avon mica district)-Continued Lemhi County__________________________________ 54 Muscovite mine-Continued Glenanprospect____________________________ 54 Reserves-Continued Valley CountY------------------------------~--- 54 Open-pit reserves___________________ 47 Panther prospect___________________________ 54 I>umps____________________________ 48 Mines and prospects in Montana_____________________ 54 Olson mine __________________________ ..:______ 48 I>istribution of known deposits___________________ 54 Silver White prospect_______________________ 49 Production and reserves_________________________ 55 Steelsmith property_________________________ 51 Mica in the Tobacco Root Mountains, Madison Location·and access_____________________ 51 CountY-------------------------------------- 55 History, workings, and production________ 51 Location and accessibility____________________ 55 Mica deposits_ _ _ _ _ __ _ __ __ _ _ _ __ _ _ _ _ _ _ _ _ _ 51 Geology___________________________________ 55 Upper tunneL______________________ 51 Pegmatites________ __ __ _______ _ _ ___ __ _ _ _ _ _ _ _ 55 Open pit, main pegmatite____________ 52 Conditions affecting mining__________________ 56 Gleason pegmatite _______ ------_____ 52 Big Chief prospect__________________________ 57 Murphy lease______________________ 52 I>ulea prospect_ _ __ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ __ _ _ 57 Tonopah north and south cuts_______ _ 52 Mci>onnellease____________________ 53 Montanarnine_____________________________ 58 Lower tunneL______________________ 53 Rim Rock prospect_ _ _ _ __ _ _ _ __ _ _ _ __ _ _ _ _ _ _ _ _ _ 59 Reserves_______________________________ 53 White Swan mine___________________________ 61 Sunshine claim_ _ _ _ __ _ _ __ _ __ _ __ _ _ __ __ _ _ __ _ _ _ 53 Vetter prospect_____________________________ 62 Witherow lease_____________________________ 54 Index_____________________________________________ 63 ILLUSTRATIONS Page PLATE 1. Maps of Avon mica district, Latah County, Idaho _____________________________________________________ In pocket 2. Map and sections of I>oerr mine and Gillis lease, Latah County, Idaho ___________________________________ In pocket 3. Map of Last Chance mine, Latah County, Idaho ______________________________________________________ Jn pocket 4. Map, plans, and sections of Luella mine, Latah County, Idaho __________________________________________ In pocket 5. Surface map of the Muscovite mine, Latah County, Idaho ______________________________________________ In pocket 6. Underground plan and sections of the Muscovite mine, Latah County, Idaho _____________________________ ln pocket 7. Geologic plans and section of stapes No. 1, 2, and 3, Muscovite mine, Latah County, Idaho _______________ In pocket 8. Open-pit mining in the Muscovite mine, and specimens of sheet mica______________________________________ 38 9. Surface map and underground workings of the Steelsmith property, Latah County, Idaho __________________ In pocket FIGURE 1. Index map of Idaho showing location of mica, beryl, and columbite mines and prospects_____________________ 9 2. Map showing location of mica prospects, Idaho and Adams Counties, Idaho________________________________ 10 3. Map showing location of Mica Queen mine, Adams County, Idaho________________________________________ 10 4. Map showing location of mica and columbite prospects, Boise and Valley Counties, Idaho____________________ 12 5. Map