UNIVERSITY OF CALIFORNIA DEPARTMENT OF MINING AND METALLURGY ASSAYING LABORATORY S. B. CHRISTY Dean LABORATORY INSTRUCTIONS FOR FIRE ASSAYS OF GOLD, SILVER, AND LEAD MINING 107 a-b WALTER S. MORLEY 4 0 Assistant Professor of Metallurgy -- 1913 -- Thesc instrncation sheets have been prrparccl in this form io take the place of mimeograph copies which were fornierly used by students electing the course in fire assaying at the University of California. These notes are concise directions for the carrying out of certain laboratory work, and in no wise cover the ground of the lectures which supplemcrlt tlie instruction in the laboratory. The purpose of the course is not to teicli merely practical fire assaying, but also to familiarize the stutlcnt with mfltilllrgical principles which underlie snlelting olwratioris on thca large scale ant1 in the lcctures as much cnipliasis is l3lccci on the underlying metallurgical principles as on tlie prcticiil tlctails of fire assaying. The laboratory work is divided into twenty-five assiglinltnts, thirteen of which arc inttntitd to cover the n-orlc of the first half-year, and the reiiairillg twelvt, the work of tliv scaoitl hitlf- .chitr. In addition to thc tz.t.lvc. assignmrnts of thv sccontl 1111- J c1ir, there will he given, as time permits, assignrncltz rrlatin to lhc firc assays of mcrcury, tin, cobalt, ancl aitirnony, alitl the determination of carbon, sulplir, ancl ash i r cm1 tulcl colte. T. IHIIE OF CONTENTS CHAPTER I PREIIJIINARY WORK PAGE 1 . Weighing ..................................................................................................... 8 2. Practice in Cupellation .................................................................. 3 . Parting Gold and Silver .................................................................. 4 . Fire Assay of Lead Bulliol .............................................................. 10 13 14 CHAPTER 11 SCORIPCATION ASSAYS 5 . Scorification in General ...................................................................... I5 G . Scarification of Silver Ores ...................................................................... 17 7 . Quartz-Gold Ores containing less than one-half Pyrite .................... 19 8 . Quartz-Gold Ores containing more than one-half Pyrite .................. 20 9 . Scarification Assay of Samples High in Copper .................................. 21 10 . Scorification Assay of Ores and Products Fusible with Difficulty . 21 11 . General Practice ........................................................................................ 22 CHAPTER I11 CRUCIBLE ASSAYS 12 . Determination of Gold and Silver in Litliarge of the Reducing Powers of Charcoal. Argol. and Flour. and Assay of Fluxes ...... 23 13 . Quartz Ores ............................................................................................ 25 14 . Nitre Assay for Ores containing Moderate Amounts of Pyrite ...... 27 15 . Nitre Assay for Ores containing Large Amounts of Pyrite ............ 20 16 . Roasting Method for Ores containing Large Amounts of Pyrite .... 30 17 . Assay of Sulphide Ores by L Nail Method ...................................... 31 . . 18 . Assay of Tailings ..................................................................................... 33 CHAPTER IV Rua. ION ASSAYS 19 . Assay of Gold Bullion .............................................................................. 35 20 . Fire Assay of Silver Bullion ........................................................ 39 CHAPTER V MISCELLANEOUS WORK 21 . Furnace Repairs . Making Cupels .................................................. 40 2 . Itfelting. liefining, and Sampling of Gold and Silver Bullion .......... 41 33 . Comparison of Methods for Assay of Copper-bearing Materials .... 42 24 . Practice in Sampling, Panning. ant1 Amalgamating .......................... 43 25 ...