The term potash refers to potassic fertilisers, which are potassium chloride (KCl or sylvite), potassium sulphate [K2SO4 or sulphate of potash (SOP), which usually is a manufactured product], and potassium-magnesium sulphate [K2SO4•2MgSO4 or either langbeinite or double sulphate of potash magnesia (SOPM or K-Mag)]. Muriate of potash (MOP) is an agriculturally acceptable mix of KCl (95% pure or greater) and sodium chloride (halite) for fertiliser use, which includes minor amounts of other nontoxic minerals from the mined ore and is neither the crude ore sylvinite nor pure sylvite.
Historically Australia has always been deficient in known resources of potash but ongoing exploration has led to published resources in recent years for some deposits such as Lake Disappointment, Lake Chandler and Dandaragan Trough/Dinner Hill deposit in Western Australia (WA), in the WA/Northern Territory (NT) portion of Lake Mackay, and in the Karinga Creek Salt Lakes area in southern NT.
Currently there are no Joint Ore Reserve Committee (JORC) Code reserves for potash resources.
Interest in exploration for potash in 2012 was largely restricted to areas with known deposits in WA and NT.
Potassium chloride is the main fertiliser product, containing an average 61% of K2O equivalent. In 2012, the main producers of potash were Canada with 9.0 million tonnes (Mt) followed by Russia (6.5 Mt) and Belarus (5.65 Mt). The three accounted for about 62% of the world production of 34 Mt, which was down from 36.4 Mt in 2011.
In Australia, some minor historic production of potash include an operation at Buladelah Mountain, New South Wales, where alunite KAl3(SO4)2(OH)6, was mined between 1890 and 1926 and again from 1935 to 1952, for a total production of 75 000 tonnes. Crude potash in form of soluble salt glaserite (K,Na)2SO4, was produced from Lake Chandler (WA) during 1943 to 1950 for a total of 9218 tonnes of glaserite.
In 1973, Geoscience Australia’s predecessor, the Bureau of Mineral Resources, reported that Texada Mines Pty Ltd was working towards becoming Australia’s first local potash producer in the form of langbeinite K2Mg2(SO4)3 at Lake Macleod in northwest WA. The planned capacity of the proposed plant was variously reported to be from 80 000 to 200 000 tonnes per annum (tpa). There is no record of production of potash from the proposed operation.
Australia imports all its potash requirements and according to the Bureau of Resource and Energy Economics1, the imports of potassium fertiliser amounted to 298 kilotonnes (kt) in 2010-11 and 290 kt in 2011-12.
According to the United States Geological Survey the countries with the largest economic resources of potash (K2O) in 2012 were Canada 4.4 gigatonnes (Gt), which represents about 46% of the total world resource, followed by Russia with 3.3 Gt (35%) and Belarus with 0.75 Gt (8%).
Lake Disappointment: Located in the Gibson Desert of WA about 320 kilometres (km) east of Newman, Lake Disappointment is a modern playa lake covering approximately 1600 square kilometres. Potash mineralisation occurs in lacustrine sediments of the lake and in the entrained brine.
On 13 March 2007, Reward Minerals Ltd published a lower estimate of 7705 Mt Indicated Resource at 3.17 kilograms per tonne (kg/t) K2SO4 containing 24Mt K2SO4 and an upper estimate of 8635Mt at 3.17kg/t K2SO4 containing 27.37Mt K2SO4. The difference between the upper and lower figure is the result of assumptions about the depth and area for the lake margins. On 30 October 2012, Reward Minerals lodged the Lake Disappointment Project Mining and Indigenous Land Use Agreement with the Native Title Tribunal for registration as an indigenous land use agreement (ILUA) between the Martu representative body Western Desert Lands Aboriginal Corporation (Jamukurnu-Yapalikunu), Holocene Pty Ltd and Reward Minerals Ltd. Reward Minerals has been granted a Mining Lease and a Miscellaneous Licence and advanced to the next phase of the project through exploration and feasibility stages.
On 9 April 2013, Reward Minerals released preliminary results from a 10 000 litre pilot evaporation trial over 180 days carried at Sylvania Station where the harvest grade/recovery figures were:
The potash minerals breakdown in the combined potash harvest were
The trial location at Sylvania Station near Newman, WA is 350 kilometres west of and on similar latitude to Lake Disappointment to provide for evaporation conditions comparable to Lake Disappointment.
The pilot scale evaporation trial at Sylvania was followed by a laboratory/pilot scale evaporation trial in Perth in late June early July 2013. The trial achieved a potassium (K) recovery of 80.2% in a harvest grading 8.06% K. The potassium yield was increased to 91.9% with a fourth evaporation stage leading to an overall harvest product grading 6.97% K for a four stage process. The low sodium chloride (NaCl) content of the harvest products at 11.5% and 9.95% NaCl respectively was considered to be important. A NaCl content of less than 20% has the potential to eliminate the flotation stage from the currently proposed flowsheet and lead to a significant reduction in the capital and operating costs for the project.
Dandaragan Greensands Project: Potash West NL is exploring the potential for producing potash from greensand deposits in the Perth Basin which are located between 50 and 230 kilometres north of Perth. The company is investigating the possibility of using conventional magnetic separation techniques to separate glauconite from greensands and is conducting field trials and laboratory scale testing to produce marketable potash products from glauconite concentrate2. On 11 October, 2012 Potash West reported an initial Indicated and Inferred Resource of 244 Mt at 3% K2O and 1.6% P2O5 for the Dinner Hill deposit containing the Molecap Greensand and the Poison Hill Greensand stratigraphic greensand units. Results of a scoping study were released by Potash West on 10 January 20133 which, according to the company, confirmed technical and financial viability for a potash production facility based at the Dandaragan Trough Project. Potash West also reported that consistently higher grades of phosphate averaging 3% P2O5 were present in the northern 30% of the Dinner Hill potash resource area and preliminary test work and economic modelling suggested that a saleable phosphate rock could be concentrated from the greensands by conventional processing steps to produce single superphosphate (SSP). The phosphate component in the samples was identified as nodular fluorapatite. The company released results of another scoping study on 19 September 20134 which suggested that a SSP production facility may be viable with a capacity for 340 000 tpa of SSP over 20 years. On 23 September 2013 Potash West released an updated resource figure for the phosphate-rich northern portion of the Dinner Hill deposit amounting to 90 Mt of Indicated Resource at 2.65% P2O5, 3.6% K2O and 4.5% CaO.
Karinga Creek Project: Rum Jungle Resources Ltd in a joint venture with Reward Minerals Ltd was analysing potassium, magnesium and sulphate levels in aquifers surrounding Karinga Creek Lakes, about 225 kilometres southwest of Alice Springs in the NT. On 9 April 2013 Rum Jungle Resources reported an Inferred Resource estimate of between 2.4 and 5.5 million tonnes of sulphate of potash at the Karinga Creek Salt Lake Potash Project, equating to a schoenite (potassium magnesium sulphate) resource of between 5.6 and 13 Mt (on a 100% basis)5. The resource is an Inferred Brine Resource estimate based on estimated upper, middle and lower ranges of porosity for known rock and sediment types. No porosity measurements have yet been taken on the sediments to accurately determine total and drainable porosity. On 18 December 2013, Rum Jungle announced that it had signed an agreement with Chinese International Chemical Consulting Corporation (CICCC) for the completion of a pre-feasibility study on the Karinga Lakes Potash Project6.
Lake MacKay: Situated in the Gibson Desert and straddling the WA/NT border 50 kilometres north of the Tropic of Capricorn, Lake MacKay is a modern, playa lake with a surface area of more than 2250 square kilometres. Reward Minerals reported in its 2009 annual report that it has delineated a JORC Code compliant Inferred Resource at Lake MacKay of 4780.4 million bench cubic metres (BCM) at 4.3 kilograms (kg) of K2SO4 (SOP) per BCM for a total of 20.56 Mt of K2SO4.
The resource estimate was calculated on the basis of lake bed sediment volume of BCM to a depth of two metres and the water soluble potassium sulphate content of the sediments that lie within the company’s tenement holdings.
The company reported in its annual report for 2012 that the next stage of development at Lake MacKay will involve infill drilling, construction of pilot ponds and pump testing as well as flow sheet development for the preparation of a project feasibility study.
Prior to committing to this phase the company has engaged in discussions with Tjamu Tjamu people and other traditional owner groups aimed at reaching agreement on terms which would be acceptable for development to proceed at Lake MacKay in the event feasibility analysis proved favourable7.
Lake Chandler: On 29 January 2009, ActivEX Limited announced a JORC Code compliant Inferred Resource of 5 779 025 tonnes at 5.73% K2O at its Lake Chandler potash deposit 45 kilometres north of Merredin and 300 kilometres east of Perth in WA. The company stated in its 2010 annual report that it carried out a scoping study on a nominal throughput of 200 000 tpa to give the project a mine life of 25 years. The company concluded that the study showed that, with the softness of the potash market, the project would be only marginal under current economic conditions.
Oxley potash prospect: On 24 April 2013, Sheffield Resources Ltd reported that they had located the Oxley potash prospect about 120 kilometres northwest of Geraldton, WA. The Oxley potash prospect is an unconventional, hard rock style of mineralisation, hosted by a unique series of ultrapotassic microsyenite lava flows which contain over 90% sanidine (potash) feldspar. Sheffield pegged about 32 kilometre strike extent of this prospective horizon within the northern portion of the Moora Basin. In their September 2013 quarterly report the company released assay results of diamond drill samples as follows: