Browsing MIRL AR Report Publications by Title
Now showing items 7-9 of 9
Resume of high capacity gravity separation equipment for placer gold recoveryThe phenomenal and meteoric rise in gold prices in the past few years has stimulated a renewed interest in domestic gold mining and many deposits once considered valueless or at best marginal at past gold prices are now potentially mineable at a profit and will become even more attractive if new and more appropriate technology can be found and applied. There have been many new innovations in gravity separation technology since the days of the gold dredge, and most of these have been developed outside of the U. S., where placer deposits are being mined and processed for various other minerals such as rutile, illeminite, zircon, cassiterite and even diamonds. Many of these newer methods could be very profitably applied to gold recovery in many present day placer or sand and gravel operations.
Solvent extraction procedure for the determination of tungsten in oresAtomic absorption methods have not been widely used for the determination of tungsten in ores due to its low sensitivity in aqueous solutions (1). A method has now been developed for solvent extraction of tungsten, making rapid determination of tungsten at low concentrations possible. It was found that tungstates, when converted to phosphotungstates, can be effectively extracted into di-isobutyl ketone (2-6 dimethyl - 4 - heptanone) (DIBK) containing Aliquat 336 (methyl tricapryl ammonium chloride from General Mills). This system was effectively used for the extraction of gold from cyanide solutioins (2). Even in aqueous solutions, phospho-tungstates give greater sensitivity (37 µg/ml for 1% absorption) compared to simple tungstates (63 µg/ml for 1% absorption). Standard tungsten solutions for extraction studies were prepared by converting aqueous solutions of sodium tungstate to sodium phospho-tungstate by boiling with ortho phosphoric acid. A Perkin-Elmer Model 303 atomic absorption spectrophotometer was used with a nitrous oxide-acetylene flame at a wavelength of 4008.75 A.
Sulphur isotopic evidence for the genesis of the Au-Ag-Sb-W mineralization of the Fairbanks mining district, AlaskaSulphur dioxide from sulphides was extracted for analysis by oxidation with Cuprous oxide at 1070º C, using essentially the method described by Robinson and Kusakabe (1975). The isotopic analyses of the purified sulphur dioxide were made on a modified Micromass 602 mass spectrometer with heated inlet system. The results were corrected for isobaric interference assuming a constant oxygen isotopic content and instrumental crosstalk (Coleman, 1977; 1980) and expressed in conventional del notation with respect to the Canon Diablo meteoritic troilite standard.