UNITED STATES DEPARTMENT OF THE INTERIOR Harold L. Ickes, Secretary GEOLOGICAL SURVEY W. E. Wrather. Director Bulletin 945-E CHROMITE-BEARING SANDS OF THE SOUTHERN PART OF THE COAST OF OREGON BY ALLAN B. GRIGGS Strategic Minerals Investigations, 1944 (Pages 113-150) UNITED STATES GOVERNMENT PRINTING OFFICE WASHINGTON : 1945 For «ale by the Superintendent of Documents, U. S. Government Printing Office, Waehington 25, D. C. Price 55 cents CONTENTS Page Abstract ................................................... 113 Introduction ............................................... 113 Location ............................................... 113 Access and transportation .............................. 114 History ................................................ 115 Field work and acknowledgments ......................... 116 Geology .................................................... 116 General features ....................................... 116 Geology of terraces .................................... 117 Chromiferous sand deposits ................................. 118 General character ...................................... 118 Mineralogy ............................................. 119 Origin and distribution ................................ 122 Reserves ............................................... 125 Mining areas ............................................... 127 South Slough region .................................... 127 Explored deposit ................................... 128 N^SWi sec. 36, T. 26 S., R. 14 W. .............. 128 Other occurrences .................................. 128 NEiNE* sec. 13, T. 26 S., R. 14 W. ............. 128 SWiNEi sec. 36, T. 26 S., R. 14 W. ............. 128 Chickamin mine ................................. 128 sec. 25, T. 26 S., R. 14 W. ................. 129 sec. 36, T. 26 S., R. 14 W. ................ 129 sec. 36, T. 26 S., R. 14 W. .............. 129 sec. 1, T. 27 S., R. 14 W. ................. 129 Terrace area north of Coquille River ................... 129 Explored deposits on the Seven Devils terrace ...... 130 Section 33 deposit ............................. 130 Section 4 deposit .............................. 132 Seven Devils (Last Chance) mine ................ 132 Other occurrences on the Seven Devils terrace ...... 135 NEj sec. 5, T. 27 S., R. 14 W. ................. 135 sec. 3 and NE£ sec. 4, T. 27 S., R. 14 W.,... 135 sec. 4, NE£ sec. 9, NW£ sec. 10, T. 27 S., R. 14 W ...................................... 136 sec. 10 and NW£ sec. 15, T. 27 S., R. 14 Vt . 136 Near center sec. 15, T. 27 S., R. 14 H, ......... 137 Explored deposits on the Pioneer terrace ........... 137 Shepard mine ................................... 137 Rose mine ...................................... 138 Eagle and Pioneer mines ........................ 138 The Lagoons .................................... 140 Other occurrences on Pioneer terrace ............... 141 Kendall mine ................................... 141 Coquille (Norman) mine ......................... 141 SE$ sec. 27, T. 27 S., R. 14 W. ................. 141 Random exploration on the Pioneer terrace .......... 141 Occurrence on Whisky Run terrace ................... 141 Pivemile Point ................................. 141 Terrace area east and south of Bandon .................. 142 Explored depos it ................................... 142 Geiger (Little) mine ........................... 142 III TV CONTENTS Page Mining areas Continued Terrace area east and south of Bandon Continued Other occurrences .................................. 142 Iowa mine ...................................... 142 Prospect 2,000 feet south of the Iowa mine ..... 143 NW£ sec. 9, T. 29 S., R. 14 W. ................. 143 NiSEi sec. 32, T. 28 S., R. 14 W. .............. 143 Pits on Crooked Creek ......°.................... 143 Denmark area ........................................... 143 Explored deposit ................................... 144 Butler (Baker) mine ............................ 144 Other occurrences .................................. 144 NW£ sec. 34, and SWi sec. 27, T. 31 S., R. 15 W. ........................................ 144 Madden mine .................................... 145 Rogue River area ....................................... 145 TSk sec. 12, T. 36 S., R. 15 W. ..................... 145 NWfc sec. 13, T. 36 S., R. 15 W. .................... 145 Present beaches ............................................ 145 General character of beaches ........................... 145 Beach deposits ......................................... 146 Beach at mouth of Fivemile Creek ................... 146 Beach at mouth of Threemile Creek .................. 146 Beach at mouth of Twomile Creek .................... 147 Beach at mouth of Johnson Creek .................... 147 Black sand occurrences in the beach near the mouth of China Creek ................................... 147 Cape Blanco beach .................................. 147 Ophir beach ........................................ 147 Rogue River beach .................................. 147 Annotated bibliography ..................................... 148 ILLUSTRATIONS Page Plate 41. Map of southwestern Oregon, showing distribution of terrace deposits containing principal chro- mite concentrations and probable sources of the chromite in them..................... In pocket 42. Geologic map of parts of the Empire and Bandon quadrangles, showing distribution of terrace deposits and chromiferous sands.......... In pocket 43. Map of the southwest coast of Oregon between the 42°20» and 43* parallels, showing distribution of chromiferous sands and upper limit of lower coastal terraces......................... In pocket 44. Exploration map and section of Section 33 chro­ miferous sand deposit.................... In pocket 45. Map and sections of the Section 4 deposit.. In pocket 46. Map and sections of the Seven Devils mine.. In pocket 47. Map and sections of the Shepard mine....... In pocket 48. Plan and section of the Rose mine.......... In pocket 49. Map and sections of the Eagle and Pioneer mines.................................... In pocket 50. Map and sections of the Butler (Baker) mine. In pocket 51. Sketch maps showing deposits of chromiferous sand in the beaches between Coos Bay and Rogue River............................... In pocket ILLUSTRATIONS V Page Figure 11. Index map of Oregon, showing locations of chromiferous sand deposits ................... 114 12. Diagrammatic sketch of layering in sand in tunnel at the Shepard mine ................... 120 13. Diagrammatic sketch of the eastern edge of the black sand deposit at the Seven Devils mine .. 134 TABLES Table 7. Partial analyses of black sands from the ter­ race area north of Coquille River ............ 121 8. Minerals in black sand deposits in the terrace area north of Coquille River ................. 122 9. Proportions of minerals in black sands from several localities, determined by count of 200 grains from each sample .................. 123 10. Percentages of magnetite, ilmenite, chromite, and zircon in samples from the black sands ... 124 CHROMITE-BEARING SANDS OF THE SOUTHERN PART OF THE COAST OF OREGON By Allan B. Griggs ABSTRACT Chromiferous sands, commonly known as "black sands" because of their color, are found both in the present beaches and on raised marine terraces along the southern Oregon coast in Coos and Curry Counties. Most of the deposits are on the lower ter­ races between Cape Arago and the town of Port Orford, and in the South Slough region. The black sand occurs in layers and lenses that range in thickness from a few inches to 42 feet, in width from a few tens of feet to more than 1,000 feet, and in length from a few hundred feet to a mile or more. The deposits on the terraces are covered with 1 to 75 feet of sand, clay, and gravel. The deposits in the present beaches are transitory, varying from year to year, and were smaller than usual and remained relative­ ly unchanged in 1942 and 1943. Besides chromite, other minerals common in the black sands include quartz, olivine, pyroxene, zir­ con, ilmenite, rutile, garnet, magnetite and epidote. Zircon constitutes 1 to 2 percent of most of the deposits, and is of definite commercial interest. Gold and platinum are present in minute quantities. The known reserves of measurable and indicat­ ed ore, minus what was mined in 1943, are 1,913,000 long tons of sand in deposits averaging more than 5 percent chromic oxide (CrgOg), and 1,212,000 long tons of sand in deposits averaging between 3 and 5 percent chromic oxide. It is estimated that 100,000 long tons of sand in the present beaches contain 5 per­ cent or more CrgO-j. The reserves in many of the deposits can be substantially increased with more detailed exploration, and other favorable regions are as yet unexplored. In 1943, two plants (one owned by Humphreys Gold Corporation and the other by Krome Corporation) began making rough chromite concentrations which were treated in a third plant constructed by the Defense Plant Corporation to produce chromite concentrates containing about 40 percent CrgOj. INTRODUCTION Location Concentrations of chromiferous sands are found in the present beaches and on marine terraces along the southern coast of Oregon. These deposits are commonly called "black sands", because of their dark gray and brown to black colors, which are due in part to the predominance of the black minerals chromite ((Fe,Mg)0.(Cr,Al,Fe)2 03), magnetite (FeFegO^, and ilmenite (PeTiOs), and in part to 113 114 STRATEGIC MINERALS INVESTIGATIONS,