QEMSCAN analysis - Example Report Cu-bearing Mill Products

Transcription

1 QEMSCAN analysis - Example Report Cu-bearing Mill Products By Dr. Katharina Pfaff Department of Geology Colorado School of Mines 1516 Illinois Street, Room 119 Golden, Colorado 841 USA kpfaff@mines.edu January 21, 13

2 Table of Contents Executive Summary...2 Project Background...3 Sample Preparation and Measurements...3 Results...4 Grain Images...4 Mineralogy...7 Particle size distribution...9 Cumulative Particle Size Distribution... 9 Grain size distribution of bornite, chalcopyrite, and covellite Locking/liberation characteristics of bornite, chalcopyrite, and covellite...11 Mineral association

3 Executive Summary In January of 13, three samples of Cu-bearing mill products were analyzed at the QEMSCAN Facility at Colorado School of Mines. One sample was a copper flotation concentrate (Cu con), one sample was of partially roasted copper floatation concentrate (Cu con part roast), and one sample was of leach residue. The copper flotation concentrate mainly consists of chalcopyrite and pyrite, with minor concentrations of FeCu sulfate, Cu-mica/Cu-clay, quartz, K-feldspar, plagioclase, muscovite, Ca sulfate, and chlorite group minerals (Tables 1 and 2, Fig. 4). The sample of partially roasted copper concentrate (Cu con part roast) consists mainly of FeCu oxide, FeCu sulfate, Fe oxides/hydroxides, and quartz. This sample also contains minor concentrations of copper sulfide minerals, cuprite, Ca sulfate, and silicate minerals (Tables 1 and 2, Fig. 4). The sample of leach residue consists mainly of FeCu oxide, Fe oxide/hydroxide, and bornite. This sample also contains minor concentrations of associated copper sulfides, cuprite, Ca sulfate, pyrite, and silicate minerals (Tables 1 and 2, Fig. 4). Particle sizes for all three samples vary from 4 μm to >1 μm (Fig. 5). Cumulative particle size distribution analysis shows the samples of partial roast and leach residue to have comparable particle size distributions (Fig. 6). Grain sizes for bornite (in volume %) range from <4 μm to 8 μm, with the majority of grains occurring in the <4 μm to 3 μm size range (Fig. 7). Grain sizes of chalcopyrite range from <4 μm to >1 μm, with most grains occurring in the 6 μm to 45 μm size range (Fig. 8). Grain sizes for covellite range from <4 μm to 15 μm, and show a bimodal size distribution (Fig. 9). is almost entirely locked in all samples, while covellite is fully locked in all samples (Fig. and 12). is dominantly locked in the partial roast and leach residue samples, but shows a range of liberation in the sample of copper flotation concentrate (Fig. 11). 2

4 Project Background In January of 13, three samples of Cu-bearing mill products were analyzed at the QEMSCAN Facility at Colorado School of Mines. The samples were named copper concentrate (Cu con), copper concentrate partial roast (Cu con part roast), and leach residue. The aims of the analyses are to: 1. Quantify the modal mineralogy; 2. Calculate the particle size distribution; 3. Calculate the grain size distribution; 4. Quantify the locking and liberation characteristics; 5. Quantify mineral associations in the samples. Sample Preparation and Measurements 1. Each sample was split into representative aliquots using a rotary micro-riffler. 2. Sized graphite was added to mitigate particle agglomeration, preferred orientation and settling. Subsequently, all samples were mounted in a 3-mm block with epoxy-resin and left to cure. 3. The blocks were ground and polished to obtain a flat surface for X-ray analysis. 4. The blocks were carbon coated to establish an electrically conductive surface. 5. The samples were analyzed at a 2.5 µm resolution in Particle Analysis (PMA) mode. 3

5 Results Grain Images Fig. 1: False color QEMSCAN image of sample Cu con. 4

6 Fig. 2: False color QEMSCAN image of sample Cu con part roast. 5

7 Fig. 3: False color QEMSCAN image of leach residue sample. 6

8 Mineralogy The sample of copper concentrate (Cu con) consists mainly of chalcopyrite (72.8%) and pyrite (15.3%). The remainder of the sample consists of minor concentrations of FeCu sulfate, Cu-mica/Cu-clay, quartz, K-feldspar, plagioclase, muscovite, Ca sulfate, and chlorite group minerals. The sample of partially roasted copper concentrate (Cu con part roast) consists mainly of FeCu oxide (54%), FeCu sulfate (12%), Fe oxides/hydroxides (6.9%), and quartz (5.1 %). This sample also contains minor concentrations of copper sulfide minerals, cuprite, Ca sulfate, and silicate minerals. The sample of leach residue consists mainly of FeCu oxide (56.3%), Fe oxide/hydroxide (9.7%), FeCu sulfate (9.1%), and bornite (8.7%). This sample also contains minor concentrations of associated copper sulfides, cuprite, Ca sulfate, pyrite, and silicate minerals. Table 1: Mineral Groups Mineral Chemical Composition CuFeS 2 Cu 5 FeS 4 Chalcocite/Digenite Cu 2 S/Cu 9 S 5 CuS FeCu Oxide Undifferentiated FeCu Oxide Cu Oxide (Cuprite) Cu 2 O FeCu Sulfate Undifferentiated FeCu Sulfate Cu Sulfate Undifferentiated Cu Sulfate Cu-mica/clay Cu-mica/Cu-clay Fe Oxide/Hydroxide Undifferentiated Fe Oxide/Hydroxide Pyrite FeS 2 Quartz SiO 2 K-Feldspar KAlSi 3 O 8 Plagioclase (Na,Ca)(Si,Al) 4 O 8 Muscovite KAl 2 (Si 3 Al)O Ca Sulfate Gypsum/Anhydrite Chlorite Clinochlore/Chamosite Others individual unidentified pixels 7

9 Table 2: Modal mineral abundance () Leach residue Cu con - part roast Cu con Chalcocite/Digenite FeCu Oxide Cu Oxide (Cuprite) FeCu Sulfate Cu Sulfate Cu-mica/clay Fe Oxide/Hydroxide Pyrite Quartz K-Feldspar Plagioclase Muscovite Ca Sulfate Chlorite Others Cu con: Minerals Cu con - part roast: Leach residue: Chalcocite/Digenite FeCu Oxide Cu Oxide (Cuprite) FeCu Sulfate Cu Sulfate Cu-mica/clay Fe Oxide/Hydroxide Pyrite Quartz K-Feldspar Plagioclase Muscovite Ca Sulfate Chlorite Others Volume (%) Fig. 4: Graphic illustration of the modal mineral abundance in in Cu con, Cu con - part roast, and leach residue samples. 8

10 Particle size distribution Cu Con Cu Con - Part roast Leach Residue < Particle size in micron Fig. 5: Particle size distribution in volume %. Cumulative Particle Size Distribution >1 Cumulative Particle Size Distribution < Particle size in micron Fig. 6: Cumulative particle size distribution curve >1 Cu Con Cu con - part roast Leach residue 9

11 Grain size distribution of bornite, chalcopyrite, and covellite < >1 Cu con Cu con - part roast Leach residue Grain size in micron Fig. 7: Grain size distribution of bornite Cu con Cu con - part roast Leach residue 15 5 < >1 Grain size in micron Fig. 8: Grain size distribution of chalcopyrite.

12 < >1 Cu con Cu con - part roast Leach residue Grain size in micron Fig. 9: Grain size distribution of covellite. Locking/liberation characteristics of bornite, chalcopyrite, and covellite A mineral is completely liberated if >9% of the particle consists only of the respective mineral. A mineral is locked if the area of the respective mineral is <3% in the entire particle, everything in between is called middling. These numbers do not reflect how easy it is to liberate a mineral by e.g., grinding the material. Analysis of liberation degree shows bornite to be fully locked in the Cu concentrate. In the partial roast and leach residue samples, most of the bornite is locked, with 3.5% and 14.5% occurring as middling s, respectively. shows a range of liberation in the Cu concentrate sample, but is dominantly locked in the partial roast and leach residue samples. is fully locked in all three samples. 11

13 Cu Con Cu con - part roast Leach residue Liberated Middling Locked Fig. : Locking and liberation of bornite Cu Con Cu con - part roast Leach residue Liberated Middling Locked Fig. 11: Locking and liberation of chalcopyrite. 12

14 Cu Con Cu con - part roast Leach residue Liberated Middling Locked Fig. 12: Locking and liberation of covellite. Mineral association Cu Con Chalcocite/Digenite FeCu Oxide FeCu Sulfate Cu Sulfate Cu-mica/clay Fe Oxide/Hydroxide Pyrite minerals Quartz K-Feldspar Plagioclase Muscovite Ca Sulfate Chlorite Others Fig. 13: Mineral associations in volume % in sample Cu con sample. 13

15 Cu con - partial roast Chalcocite/Digenite FeCu Oxide Cu Oxide (Cuprite) FeCu Sulfate Cu Sulfate Cu-mica/clay Fe Oxide/Hydroxide minerals Pyrite Quartz K-Feldspar Plagioclase Muscovite Ca Sulfate Chlorite Others Fig. 14: Mineral associations in volume % in sample Cu con part roast. Leach Residue Chalcocite/Digenite FeCu Oxide Cu Oxide (Cuprite) FeCu Sulfate Cu Sulfate Cu-mica/clay Fe Oxide/Hydroxide minerals Pyrite Quartz K-Feldspar Plagioclase Muscovite Ca Sulfate Chlorite Others Fig. 15: Mineral associations in volume % in leach residue sample. 14

16 The mineralogical data reported in this study directly reflect the best possible analysis of the materials provided. All efforts were made to ensure the highest level of quality control for the materials provided. Certain factors beyond the control of this laboratory may include: sample selection and representivity of materials, sample preparation by other laboratories, small sample size, small grain size close to the resolution of the system, and statistical representation of trace phases. The QEMSCAN Facility is not responsible for any further interpretation or application of the data other than that contained herein, and application to larger sample populations may not be valid without further analysis. Information regarding laboratory operations, quality control and quality assurance is available on request. 15