| Discovery |
| Tenements |
| Mining and Treatment |
| Mining History |
| Environment |
See also "maps" page for mine locations.
DISCOVERY
Small tonnages of low grade gypsum south of Meningie were reported by the South Australian Deputy Government Geologist in 1921. Sean Kennedy and Jeff Olliver checked the location in 1995 and found high grade gypsum with a potential for large tonnages.
We used push tubes and hand augers to explore the gypsum deposits. This is low technology and is environmentally friendly. Hundreds of samples were taken, and the majority were analysed for gypsum content. Exploration still continues after five years and our resources of gypsum currently stand at about 9 million tonnes.
The close spacing of drillholes allowed accurate mapping of each gypsum deposit with respect to thickness, grade, and the calculation of tonnages.
TENEMENTS
All the gypsum deposits discovered in the Meningie area since 1995 are now held by Meningie Gypsum Pty Ltd as Mining Leases and Exploration Licences. These areas are shown on the maps page.
MINING AND TREATMENT
There is no overburden. The gypsum occurs from the surface to a depth of about 1.5 metres. Mining is by excavator, with dump trucks delivering to the stockpile site. At Elephant Lake selective mining has enabled separation of the top 0.3 metres, consisting of ultrafine gypsite, from the underlying slightly coarser but purer gypsarenite.
The freshly mined and stockpiled gypsum contains small amounts of sodium chloride. Draining of wet freshly mined gypsum in stockpiles, with additional leaching by rainwater, lowers the salt content. All gypsum sold has well below the permissible maximum of 2% salt for agricultural use.
After leaching and drying the stockpiled gypsum is power screened to -10mm.
MINING HISTORY
Mining commenced in December 1997 at the Gemlake deposit 6km south of Meningie. Gemlake is only 200 metres west of the Princes Highway, the main coastal route between Adelaide and Melbourne. It is concealed from the highway by trees and a sand dune. This deposit of about 50 000 tonnes is particularly rich, with gypsum grades exceeding 90%.
Another minesite opened in January 1999 at Elephant Lake, 13km northeast of Meningie. This required considerable development work, such as the building of a three kilometre haul road to connect the stockpile site to the nearest public road. Elephant Lake contains 1.4 million tonnes of high grade gypsum.
ENVIRONMENT
All the gypsum occurs in lake beds which are either completely bare or have a thin samphire cover. By mining the gypsum, the water table becomes exposed. Evaporation then lowers the water table, not only in the lakes being mined, but also in the surrounding farm land. This has the beneficial effect of counteracting the rising salinity of these farm lands. Increasing salinity has been a problem for several years in the Lower Murray Basin.
Home
Mining