Heavy Mineral Concentrates Why HMC Heavy minerals can be concentrated from glacial till samples or from stream sediments The theory behind the use of heavy mineral concentrates relies on the fact that by concentrating the heavy mineral fraction from the sample the dilutant light minerals which may obscure an an oma ly derived from a deposit are eliminated providing a clearer picture This allows the minerals to be examined under a binocular m i c r o s c o p e S E M o r e l e c t r o n m i c r o p r o b e f o r p a r t i c l e s h a p e o r composition Particle shape of gold grains will commonly identify distance to source V ery abraded grains may have travelled a good distance whereas delicate grains are probably more local Similarly for diamond exploration the presence of certain mineral phases may indicate distance to source kimberlites Bulk analysis of heavy minerals provides a rapid low cost method to screen large volumes of samples Samples with appropriate chemistry can then be further evaluated as the INAA technique is nondestructive Heavy mineral concentrates are usually prepared by tabling or wet sieving a very large sample of till or stream sediments up to 20 kg may be routine The heavy mineral concentrate collected at this stage is then further processed with heavy liquids using methylene iodide SG 33 The resultant concentrate then is separated into magnetic and non magnetic fractions and it is the nonmagnetic fraction which is usually analyzed In some cases more elaborate separations include separating paramagnetic fractions and sieving to various particle sizes before analysis This may provide further insight into identifying the source of the heavy minerals Both gold and diamond mines have been discovered using this technology HMC Thermal HMC Base Metals Code 3A Code 3C Ag 5 02 As 2 Au 5 ppb Ba 200 Br 5 Ca 1 Cd 05 Ce 3 Co 5 Cr 10 Cs 2 Cu 1 Eu 02 Fe 002 Hf 1 Hg 5 Ir 50 ppb La 1 Lu 005 Mn 2 Mo 20 2 Na 005 Nd 10 Ni 200 1 Pb 2 Rb 50 S 100 Sb 02 Sc 01 Se 20 Sm 01 Sr 02 Ta 1 Tb 2 Th 05 U 05 W 4 Yb 02 Zn 200 1 All elements are in ppm except where noted Code 3A Heavy Mineral Concentrates Thermal Irradiation Heavy mineral concentrates prepared from reverse circulation drilling samples or from panned concentrates are expensive to collect The nugget ef fect may require that the entire sample be analyzed to ensure that the few particles of gold w hich may be present can be measured With INAA the whole concentrate can b e analyzed without grinding the samples The sample is therefore preserved for other chemical or mineralogical work Actlabs only irradiates with thermal neutrons so as to avoid low gold values due to self shielding ef fects from irradiation with epithermal neutrons The price varies depending on the volume of concentrate to be analyzed There are 3 vial sizes available small 2 g medium 20 g or large 60 g Actual weight may vary depending on mineralogy Code 3C HMC Base Metals by Aqua Regia ICP When the analyses by INAA are completed the sample is available to determine additional elements by other analytical techniques Code 3C is a frequently requested Aqua Regia extraction ICPOES package 05 g required First element price for Code 3C is 600 with each additional element costing 200 Code 3C may require the sample to be pulverized finer if coarser than 80 mesh 175 micron at an additional cost Prices Small vial 2 g 1900 1 100 Medium vial 20 g 2100 Large vial 60 g 2600 P AGE 34