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Geology and Ore Deposits of the Index Mining District

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Geology and Ore Deposits of the Index Mining District W.A.SH1NGTON GEOLOGICAL SURVEY HENRY LANDES, State Geologist BULLETIN No. 7 Geology and Ore Deposits of the Index Mining District By CHARLES E. WEAVER OLYMPIA, WASB.: E. L. BOARDMAN, PUBLIC PRINTER 1912 BOARD OF GEOLOGICAL SURVEY. Governor M. E. HAY, Chairman. State Treasurer J. G. LEWIS, Secretary. President T. F. KANE. President E. A. BRYAN, HENRY LANDES, State Geologist. SOLON SHEDD, Assistant State Geologist. LETTER OF TRANSMITTAL. Governor M. E. }lay, Chairman, and Members of the Board of Geol,ogical Survey: GENTLEMEN-I have the honor to submit herewith a. report entitled "Geology and Ore Deposits of the Index Mining Dis­ trict," by Charles E. Weaver, with the recommendation that it be printed a.s Bulletin No. 7 of the Survey reports. Very respectfully, HENRY LANDES, State Geologist. University Station, Seattle, December 1, 1911. CONTENTS. Page ILLUSTRATIONS 7 lNTROOUC'l'.ION • • • • • • • • • • • • • • • • • . • . • • • • • • • • • . • . • . • • • • • • • • . • • • • 9 Field work and acknowledgments.......... .................. 9 Location and area of th.e district. 10 Industries and settlements. 12 Literature . 14 CHAP'fER I. PHYS(OGRAl'lIY. • • • . • . • . • • • • • . • • • . • • . • • . • • . 21 Topography . 21 General statement . 21 Drainage . 22 Forms of the surface...................................... 24 Glaciation . 25 Climate . ... 28 Vegetation . 29 Relation of present topography to general geology. 30 CHAPTER II. GENERAL GEOLOGY. • • • • . • . • . • • • • • • • . • . • . • . • 34 General statement . 34 Gu.nu Peak formation. 35 Areal distribution . 35 General description . 36 Thickness . 37 Correlation and age....................................... 37 Granodlorite . 38 Areal distribution . 38 Petrograpby . 39 Contact relations . 42 Granodlorite aplite . 43 Andesite porphyry dikes...................................... 44 West Index andesitlc series................................... 44 Areal distribution . 44 General description . 45 Correlation . 45 Howard a1·kose formation. 46 General description . 46 Areal distribution . 46 Correlation . .. 47 Olivine diabase . .. 47 Quaternary . 48 Glacial drift . 48 Alluvial deposits . 49 Talus deposits . 49 Structure . 49 Geological history . 51 6 Contents Page Cl:UPTER III. ECON01'll0 GEOLOGY. • • . • . • . 64 History of mining. 64 Treatment of the ores........................................ 56 Production . 57 Distribution of the ore bodies. 57 Character of the ore bodies............................ .. ... 68 Strike . 58 Pitch .......................... ................... .... 69 Shape .................................. .. .............. 69 Influence of the country rock on the ores ..................... 59 Alteration of the country rock ............................... 60 Mineralogy ........................ ............... ... ..... 62 Genesis of the ores .......................................... 66 Placers .................................................... 70 CJUPTEB IV. DETAILED DESCRIPTION OF TBE MINES................. 71 General statement . 71 Sunset mine . 71 Non-Farell mine . 73 Ethel Consolidated mine. 74 Kittanning mine . 76 Merchant mine . 77 Homestead mine . 79 Co-operative mine . 79 Lost Creek mine. 80 Uncle Sam mine .......................................... : .. 81 Calumet mine . .. 82 Florence-Rae mine . 83 Bitter Creek mine............................... ........... 84 Index Bornlte mine.......................................... 84 Index Peacock mine. 85 Gunn Peak mine............................................. 86 Helena mine . 86 North Star mine. 86 Index Independent mine.. .................................... 87 Buckeye mine . 88 Copper Bell mine. 90 Red Cross mine.............................................. 92 Index granite quarry. 92 Halford granite quarry . 93 ILLUSTRATIONS. 0J)J)080fl Paq, I. Outline map of a portion of Washington, showing the position of Index District. 10 II. Geologic map of Index District. 40 III. Horizontal plan showing mine workings of Ethel mine. Plan and cross-seceion B-B' of Non-Farell mine............... 72 IV. Horizontal plan showing mine workings of the Bunker Hill mine .................................................. 72 V. Cross-section A-A' of mine workings of Ethel mine. Cross­ section G-G' of Bunker Hill mine. Horizontal plan of mine workings of North Star mine. Plan of mine work­ ings of Merchant mine.. 80 VI. Horizontal plan and c~oss.sectlons E-E' and F-F' of the Sun­ set mine. Plan and cross•sectlon C-C' of the Index M1nlng Company's mine. Horizontal plans of Index Bornlte mine and Buckeye mine..................................... 80 VII. Map of mining claims of Index Mining District.. 88 INTRODUCTION. FIELD WORK AND ACKNOWELDGMENTS. Geological field work in the Index Mining District was begun on August ~nd, 1910, and continued until September ~0th of the same year. During this time the large1· part of the areal geological mapping was completed, and many of the detailed underground examinations of the ore deposits were made. Later, during the autumn months of the same year, several shorter trips were undertaken for the pm-pose of completing the geological mapping and the examination of the individual mines. Mr. Charles R. Fettke assisted in surveying the trails as well as many of the tunnels and open cuts. He also assisted in the areal geological mapping and in some of the under­ ground studies. The ore samples ta.ken from the various min­ ing properties were assayed by Professor C. R. Corey, of the College of Mines of the University of Washington. The topographic map which is used as a base for repre­ senting the areal distribution of the geological formations occurring within this district was in part constructed from a photographic enlargement of a portion of the Skykomish quad­ rangle, published by the U. S. Geological Survey, and in part from the Snoqualmie topographic atlas made by the Forest Service of the United States Department of Agriculture. The former was enlarged from a scale of one-half inch to the mfle, to a scale of one inch to the mile, and the Forest Service map, which already existed on the scale of nearly one inch to the mile, with ~00-foot contours, was made to conform to it. The 10 Bulletvn No. 7, Washvngton Geological Survey resulting map is on a scale of one inch to the mile w:ith 100- foot contours. Wherever possible foot and compass s1uveys were made of the trails, and the cabins, mine openings and vein outcrops were tied in to some definitely located monument. Wherever mining maps, showing the plan of the underground workings, were not available, an attempt was made to construct them as accurately as.
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