This follows exhaustive quality testing of a bulk sample of the nominally 97% topaz concentrate by an international abrasives supply company as a high-pressure water cutting abrasive feedstock.
The material supplied by Chase is representative of what would be produced by a proposed gravity recovery plant from the present flowsheet with a minus 1 mm silexite feed from Torrington.
Air separation could be a commercial option
The main product quality condition that must be met is the optimisation of the topaz concentrate to ensure that its free silica (quartz) content is < 1% to meet respiratory heath concerns to ensure a saleable abrasive product is produced.
Chase has been undertaking topaz concentrate clean-up (free silica / quartz removal) test work to meet this requirement.
However, these and other laboratory successes have not proven economically viable on a commercial scale given the relatively low value of abrasive products.
In a recent development in conjunction with Chris Browne who is a consultant extractive metallurgist it was decided that air separation may work on the dried 0 to 1 mm spiral topaz concentrate product to remove the quartz given its density is 2.65 and that of topaz is 3.55.
Contact was made with Satake Australia in Penrith who produce air gravity tables for grain and other seed cleaning purposes and they completed non-quantitative test work on the topaz using a small demonstration plant they have on site.
Satake air gravity table test work
Although not optimised for mineral separation, it was clear that the dark coloured impurities (tungsten and monazite) reported to the top of the table and the quartz to the bottom portion.
Microscope studies of the samples indicate that the topaz concentrate is largely free of quartz although there are remaining dark metallic impurities.
The samples were not processed though magnetic separation to remove those impurities.
Future planned test work
These initial and very basic tests indicate that air separation may be a commercial option for the removal of the free silica (quartz) content of the topaz concentrate to below 1%.
However, the yield can probably be considerably increased by repassing the balance of the topaz over a second table.
A commercial size air table has been built and will be available to optimise the test work at a future date.
Newly constructed commercial size air gravity table