Annual Report GR427 Florina Project for the period 30 July 2015 to 29 July 2016

Abstract

Florina Formation consists of two glauconitic sandstones sandwiched between dolostones. The lower glauconitic sandstone (LGS) is 68 metres thick as determined by water bore drilling. Geological mapping indicates the LGS is mostly free of the overlying Cretaceous sandstone, and presents numerous solitary outcrops in river banks and colluvial plains where it is conspicuously green with up to 40% glauconite. Mineralogical and chemical sampling has focused on the LGS in EL 30603. A collection of 10 grab samples from the bank of the Daly River (EL 30603 only) have been subject to a combination of XRD analysis, crushing screening with magnetic separation, and XRF analysis of both whole-rock and glauconite concentrates. The sandstones contain rounded glauconite grains 0.2-0.8mm in diameter, and sub-angular detrital quartz grains 0.1-0.4mm in diameter, as the major components. The absence of carbonates and potash feldspar indicated K2O and Fe2O3 can be used to estimate modal content of glauconite, which in this collection averages 37%. Trial magnetic separation on four crush sizes (+500, 280-500, 106-280, and less than 106 micrometre) at various magnetic settings showed a clean concentrate can be achieved with grind size 106 - 280micrometre with magnetic field setting of 9400 Gauss. SEM EDS analysis showed that most glauconite grains contain abundant inclusions of apatite (phosphorite) at the micron scale. Initial estimate of the chemical composition of the glauconite concentrate is 7.45% K2O and 2.65% P2O5. Preliminary kinetic leach tests on glauconite concentrate using sulphuric acid and citric acid were done by the CSIRO. Ring-grinded P80 25 micrometre concentrate achieved a high 40% potassium extraction after eight hours with hot citric acid, comparable to that for hot sulphuric acid. This enhanced dissolution with ring-grinding may be due to mechanical activation. A larger composite sample of sandstone of about 37% glauconite content was crushed to P80 106 micrometre and deslimed at 38 micrometre. It yielded 12kg of high-quality concentrate. This was thermally activated and subject to both standard fertilizer analyses at ambient temperature and kinetic leach tests at elevated temperature. NAC (neutral ammonium citrate) analyses showed a twelve-fold increase in potassium release from activated glauconite relative to non-activated glauconite. Similarly CA (5% citric acid) analysis indicated full release of potassium may be achieved over an annual plant growing cycle. Follow-up kinetic leach tests were conducted on activated glauconite over an extended period of 48 hours at 950C, on size fractions of 48 micrometre-106 micrometre, and P80 38 micrometre. Both size fractions showed near- 100% dissolution of both potassium and phosphorus over periods of 48-60 hours. Leach results 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. Further kinetic leach tests will be required to optimize the extraction of potassium in terms of temperature, acid strength, leach time, grind-size, and catalysts. Such tests would define the preferred product path. Drilling is now required to define a resource, and provide material for further metallurgical and chemical tests.