Annual Report GR427 Florina Project for the period 30 July 2017 to 29 July 2018

Abstract

The Florina Potassium-Phosphate Project is based on the Ordovician Florina Formation in the Daly River Basin, which contains glauconite-rich sandstones. Glauconite is a potential source of potassium fertiliser with phosphate credits, suitable for local and national agricultural use. The project is centred on Florina Pastoral Station 70 km west of Katherine. Florina Formation consists of two glauconitic sandstones sandwiched between dolostones. Two cored PQ holes drilled into the lower sandstone at localities 5 km apart, define a 19-meter thick glauconite rich unit (GRU) at the top of the lower sandstone, for which logs and photographs are available. Unfortunately cores were lost whilst in transit to the metallurgical laboratory, so no mineralogical, geochemical or geotechnical information is available. Detailed mapping shows the GRU extends as a gently undulating flat-lying unit over an envelope of 102 km under shallow regolith in the middle reaches of Yujullowan Creek on EL 30603. The GRU presents an exploration target of 400Mt at an estimated grade in the range of 25-35% glauconite. A concentrate of grind size 106 - 280 micrometre can be achieved by WHIMS, although a cleaner circuit is required as well as a rougher and scavenger. The GRU glauconite is geologically unique in that most grains contain abundant inclusions of apatite (phosphorite) at the micron scale. Grab samples and small bulk samples Initial estimate of the chemical composition of the glauconite concentrate is in the range of 7.5 - 9.5% K2O and 2.65% P2O5. Glauconite can be activated in a proprietary flash reactor such that potassium and phosphorus can be leached by cold dilute acids. Activation involves de-hydroxylation which preserves grain integrity and crystal structure, improves specific surface area, and involves loss on ignition. Customised CA (citric acid) fertiliser analyses involving cold 5% citric acid over 28 days indicated potential for a slow-release potash fertiliser. This was confirmed by 112-day kinetic leach tests on air-activated material from the first activation campaign, which gave 45% dissolution of potassium. Follow-up 224-day kinetic leach tests were conducted on a cleaned concentrate from a second activation campaign in steam medium, at CA concentrations of 2% and 5% and different residence times. This showed greatly enhanced (six-fold) dissolution of potassium compared to a non-activated control sample. This achieved 45% potassium dissolution after 224 days, which is the same extraction as the air-activated material after 112 days. This suggests better activation, as measured by better dissolution rates, is achieved with a single pass (residence time of about 7secs) in a medium of air (as distinct from steam), at the relatively low temperature of 6200C. Leachability is independent of grain size. In all cases, irrespective of activation parameters or citric acid concentration, phosphorous dissolves early and fully, even for the non-activated glauconite. Clearly selective extraction of phosphorous as phosphoric acid is possible. The 224-day kinetic leach tests also showed that the levels of dissolution of the ancillary elements iron, magnesium and aluminium were significantly less (circa 20%) than that for potassium, giving some encouragement that selective leach can be achieved with cold dilute organic acid. This points to the necessity to undertake a controlled program of selective leach and precipitation (SLAP) tests. Leach results continue to demonstrate Florina glauconite may deliver either a slow-release potassium fertiliser with phosphate credits, or feedstock for industrial potash with phosphate and sulphates as by-product. Such fertiliser products would not require complex and expensive process routes involving hot mineral acids. This is an innovative processing route that is the subject of an Australian Patent application called Method of Producing Potash Fertiliser from a Mica Source.