DEPARTMENT OF THE INTERIOR UNITED STATES GEOLOGICAL SURVEY GEORGE OTIS SMITH, DIRECTOR BULLETIN 445 GEOLOGY OF THE PEGMATITES AND ASSOCIATED ROCKS OF MAINE INCLUDING FELDSPAR, QUARTZ, MICA, AND GEM DEPOSITS BY EDSON S. BASTIN WASHINGTON GOVERNMENT PRINTING OFFICE 1911 CONTENTS. Introduction.............................................................. 9 Definition of pegmatite...................................................... 10 Geographic distribution.................................................... 10 Geology.................................................................. 10 Bordering rocks....................................................... 10 Pegmatites in foliated rocks........................................ 11 General statement............................................ 11 Sedimentary foliates........................................... 11 Igneous foliates.....".......................................... 12 Pegmatites in massive granites.................................... 13 'Age.................................................................. 15 General character..................................................... 15 Mineral and chemical composition................................. 15 Mineral constituents.......................................... 15 Relative proportions of minerals............................... 18 Quartzose phases. ..............................^............. 18 Fluidal cavities............................................... 19 Sodium and lithium phases................................... 20 Muscovite phase............................................... 22 Texture.......................................................... 22 Irregularity of grain.......................................... 22 Graphic granite.............................................. 22 Feldspar brushes............................................. 23 Intergrowths of minor constituents............................. 25 Mica......................................................... 26 Gem-bearing pegmatites....................................... 26 Origin of the Maine pegmatites......................................... 27 Relations to granites............................................... 27 External conditions............................................... 28 Dominant constituents..................................... 1...... 28 Minor constituents................................................. 29 Gaseous constituents.............................................. 30 Viscosity and gas content. ............... i... .\.................... 32 Miarolitic cavities............................................ 32 Contact-metamorphic effects.................................. 33 Forms of the intrusives....................................... 35 Temperatures of pegmatite crystallization .......................... 36 Experiments of Wright and Larsen............................. 36 Application to Maine pegmatites............................... 39 Eutectics in pegmatites........................................... 39 Mineralogical provinces........................................... 43 Geographic relations.............................................. 43 Summary........................................................ 45 3 4 CONTENTS. Page. Local descriptions.................................................... 1.... 46 Androscoggin County.................................................. 46 Auburn........................................................... 46 Character and distribution of the pegmatites..................... 46 Auburn Falls............................................. 46 Auburn reservoir.....................................:.... 46 Danville Corners.......................................... 47 Danville Junction......................................... 48 Mount Apatite............................................ 49 Quarries..................................................... 50 Maine Feldspar Company quarry and mill................... 50. Turner feldspar quarries.................................. 54 Towne feldspar and gem quarry.............................. 55 Wade and Pulsifer gem quarries............................ 56 Minot............................................................ 59 Poland. .......................................................... 59 Cumberland County................................................... 61 Brunswick....................................................... 61 Westbrook....................................................... 62 Hancock County...................................................... 63 Lincoln County....................................................... 63 Edgecomb......................................................... 63 Edgecomb feldspar quarry...................................... 63 Geologic relations..................................:.......... 64 Boothbay Harbor................................................. 64 Character and relations of the pegmatites....................... 64 Schists associated with pegmatites.............................. 68 Syenite porphyry............................................. 69 Oxford County......................................................... 70 Albany........................................................... 70 French Mountain beryl locality................................ 70 Bennett mica prospect......................................... 70 Pingree mica prospect......................................... 70 Andover........................................................... 71 Buckfield.. ..........^............................................ 71 Greenwood........................................................ 71 Hebron............'................................................ 72 Hibbs feldspar and mica mine................................. 72 Mount Rubellite............................................... 74 Streaked .Mountain............. ............................. ... 74 Mills feldspar quarry.......................................... 75 Newry ............:....:......................................... 76 Norway.......................................................... 78 Paris............................................................. 79 Hill north of Crocker Hill....................................... 79 Mount Mica...............................................'.... 81 History.................................................... 81 Gem-bearing zone.......................................... 83 Pockets................................................... 85 Minerals.................................................. 86 Gems..................................................... 89 Production a.\d method of mining.......................... 92 Peru............................................................. 93 CONTENTS. 5 Local descriptions Continued. Oxford County Continued. Page. Rumford........................................................... 93 Vicinity of Rumford Ealls...................................... 94 Black Mountain mica mine........................... ; ........ L 95 Standish................:................:.........:.............. 98 Stoneham........................................................ 98 Geology...................................................... 98 Gem localities........................................... ..... 98 Sugar Hill................................................ 99 Harndon Hill............................................. 100 Stow.............................................................. 102 Waterford........................................................ 102 South Waterford mica mine..................................... 103 Beech Hill mica mine......................................... 104 Sagadohoc County..................................................... 105 ' Georgetown....................................................... 105 Georgetown Center............................................ 105 Hinckleys Landing............................................ 105 Goldings feldspar quarry ....................................... 105 Small Point feldspar quarry..................................... 108 Schist-pegmatite contacts on Bay Point Peninsula................ 108 Topsham......................................................... 109 Distribution of the quarries..................................... 109 Products of the quarries........................................ 110 Mount Ararat feldspar quarries................................. 110 Fisher's feldspar quarry....................................... 112 William Willes feldspar quarry.................................. 113 Maine Feldspar Company's quarry............................. 115 G. D. Willes feldspar quarry.................................... 115 North Topsham feldspar quarry................................ 116 Mill of Trenton Flint and Spar Company ....................... 117 Vicinity of Topsham village.................................... 117 Economically important pegmatite minerals................................. 119 Feldspar.............................................................. 119 Potash-soda feldspars.............................................. 119 Lime-soda feldspars or. plagioclases................................. 120 Graphic granite..................;................................. 124 Mining............................................................ 125 Commercial availability of deposits................................. 126 Milling..........................................................:' 127