DEPARTMENT OF THE INTERIOR UNITED STATES GEOLOGICAL SURVEY GEORGE OTIS SMITH, DIRECTOR 4:05 THE MERCURY MINERALS FROM TERLINGUA, TEXAS BY W. F. HILLEBRAND AND W. T. SCHALLER WASHINGTON GOVERNMENT PRINTING OFFICE 1909 CONTENTS. Page. Introduction.............................................................. 7 Occurrence and associations of the minerals.................................. 8 Geologic occurrence .................................................... 8 The matrix............................................................ 9 Associations............................................................ 10 Kleinite........................................................... 10 Montroydite...................................................... 10 Terlinguaite. ..................................... ^............... 11 Eglestonite....................................................... 11 Calomel........................................................... 11 Mercury........................................................... 12 Summary.......................................................... 12 Introduction to crystallography.............................................. 12 Nonmercury minerals ..................................................... 15 Calcite............................................................... 15 Gypsum...................... '. ........................................ 16 Barite................................................................. 17 Jarosite................................................................ 17 Mercury minerals..........................'................................ 18 Kleinite............ 1.................................................. 18 History............................................................ 18 Modes of occurrence................................................ 20 Physical properties................................................ 20 Cohesion, etc.......................'........................... 20 Density....................................................... 21 Luster, color, etc.............................................. 21 Optical properties.............................................. 23 Chemistry......................................................... 27 General characteristics......................................... 27 Quality of the material.................................... 27 Fyrognostic characters..................................... 27 Qualitative behavior toward reagents........................ 28 Additional data............................................... 28 Data relating chiefly to. oxygen, nitrogen, and chlorine....... 28 Data relating to water and hydrogen........................ 32 Aiialytical methods employed and the results..................... 33 Nitrogen.. ................................................ 33 Mercury................................................... 37 Chlorine and sulphur....................................... 38 Gangue, water (hydrogen?).................................. 39 Analysis.................................................. 40 Discussion of analyses..................................... 42 Crystallography................................................... 43 Forms and value of c axis.. ...'................................. 43 Habit........................................................ 45 Summary.......................................................... 46 3 4' CONTENTS. Mercury minerals Continued. Page. Montroydite.........................................:................ 47 Forms............................................................. 47 Physical properties. ................................................. 52 Cohesion, etc.................................................. 52 Flexibility..................................................... 53 Density....................................................... 54 Luster, color, etc.............................................. 54 Optical properties.............................................. 55 Chemistry......................................................... 55 Crystallography................................................... 56 General description........ 1.................................... 56 Calculation of elements................................ 4 ........ 57 Forms and angles............................................. 59 Description of common forms.................................... 61 Description of less common forms...................... '......... 65 Description of rare forms........................................ 68 Summary of forms.............................................. 68 Discussion of forms.............................................. 69 Combinations................................................. 73 Zonal relations, striatious, and gnomonic projection of forms ...... 74 Habit........................................................ 75 Description oi crystals.....................................:.... 78 Terlinguaite.......................................................... 83 Forms............................................................. 83 Physical properties................................................ 83 Cohesion, etc................................................... 83 Density....................................................... 84 Luster, color, etc.............................................. 84 Optical properties.....................'......................... 85 Chemistry......................................................... 86 Pyrognostic behavior.......................................... 86' Behavior toward reagents...................................... 86 Quantitative composition...................................... 87 Crystallography..................'................................. 88 General description.....:....................................... 88 Calculation of elements......................................... 89 Forms and angles............................................... 93 Description of common forms.................................... 96 Description of less common forms............................... 98 Description of rare forms........................................ 107 Doubtful and vicinal forms..................................... 108 Discussion of forms............................................ 110 Combinations................................................. 121 Zonal relations and gnomonic projection.......................... 124 Habit........................................................ 125 Description of crystals.......................................... 126 Different orientations and transformation symbols................ 132 Coordinate angles arranged in order of increasing (f> value......... 137 Forms and corresponding angles with (010) as pole............... 140 Eglestonite........................................................... 143 Forms............................................................. 143 Physical properties................................................ 144 Cohesion, etc.................................................. 144 CONTENTS. 5 Mercury minerals Continued. Eglestonite Con tin ued. Physical properties Continued. Page. Density....................................................... 144 Luster, color, etc.............................................. 144 Optical properties..........................................:... 144 Chemistry......................................................... 145 Pyrognostic behavior.......................................... 145 Behavior toward reagents...................................... 145 Quantitative composition....................................... 145 Crystallography................................................... 147 General description............................................. 147 Forms and angles............................................... 147 Description of common forms.................................... 149 Description of less common forms............................... 149 Description of rare forms........................................ 151 Discussion of forms............................................. 151 Combinations.................................................. 152 Zonal relations and gnomonic projection........................ 154 Habit........................................................ 155 Description of crystals.......................................... 156 Calomel.............................................................. 157 Forms............................................................. 157 Physical properties................................................ 158 Cohesion, etc................................................... 158 Density....................................................... 158 Crystallography................................................... 158 Previous publication.......................................... 158 General description............................................. 158 Calculation of elements......................................... 159 Forms and angles............................................... 160 Description of forms........'.................................... 161 Discussion of forms. ................. ^........................... 165 Combinations................................................... 166 Habit........................................................ 167 Twin crystals..............."................................... 167 Description of crystals.......................................... 168 Form system.............'.....................................