AST Sand Mines announces a “maiden” quartzite resource, strategically located to supply roadstone and silica sand to the infrastructure and construction sectors in East Pretoria and the Moloto corridor in KwaMhlanga
Van Dykspruit quarry, owned by AST and located on the Gauteng and Mpumelanga provincial border, declared its maiden quartzite-roadstone resource recently as management initiated their inaugural blast to access the underlying high grade quartzite rock. The quartzite will be processed to supply roadstone to the nearby Moloto corridor project in KwaMhlanga.
The quarry, which has been in operation since 2012, has to date been extracting a surface level resource of weathered sandstone which is processed with state-of-the-art wet screens that produce high grade silica which is supplied to clients such as Petra’s Cullinan diamond mine for use in underground structural concrete.
AST’s managing director, Ian Ross, said: “We have developed this mine over the past 7 years from a greenfield start, to become a fully operational quarry that is now positioned to become a strategic supplier of roadstone and high grade silica for the construction and infrastructure market in North and East Pretoria, and KwaMhlanga.”
Current production capacity is 30 000 tonnes per month, and the mine is delivering a 98% silica sand product, with run-of-mine passing 8mm and 13% passing 75μ. After processing, the mine’s standard grade of product is delivered at -8 mm /+75μ, carrying an average 2.5% of sub 75 μ material, which allows clients to receive a consistently graded product at volume which is suitable for making high grade structural concrete.
An extensive drilling programme and high-resolution, low-frequency Loza ground-penetrating radar survey has been completed. The resource will meet East Pretoria and KwaMhlanga’s demand for roadstone for close to a decade. Ross said: “We have been able to drill the quartzite resource with a high degree of accuracy using a new ground penetrating radar technology. This has allowed us to delineate the resource at a low cost. The recovered core has been confirmed as a high grade roadstone, and allowed us to optimise the design of the crushing circuits that will deliver the scope of material the market demands.”
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AST retained B&E International to conduct the inaugural drilling, and the inaugural yielded over 50 000 tons of product immediately available. Ross said, “We are now the closest operational quarry to Moloto, and we look forward to working with our clients and partners to deliver value as the Moloto development gets underway.”
About AST: Website: www.ast14.co.za
AST’s Silica & Quartzite Mines
AST’s quarry mine is in production exploiting near-surface semi-consolidated sandstone lithologies. This resource sits in a small package that is a remnant of the Ecca group, consisting of sandstone, that itself overlies the Loskop formation that consists of quartzites that are a target resource for roadstone.
The silica is processed in a dry screen, and then into a wet screen. The wet screen technology, sourced from CDE in Ireland (www.cdeglobal.com) , delivers a consistent high-quality product.
The washing system produces concrete sand (coarse) and plastering sand (fine), but it can also produce a single plastering sand or concrete sand in larger quantities as required by the customer. The washed sand product is typically less than 2.6% moisture content (by weight) which ensures it is suitable for use immediately.
Environmental considerations are central to ASTs approach. The wet-screen’s waste-water treatment process reduces the volume of fresh water to feed the washing plant by over 90%. This represents a huge reduction in water usage, and the plant design is confined to a much smaller plant and mining operation “footprint” of circa 30m x 20m.
A crushing circuit will be installed and commissioned to process the quartzite at 400 tonnes per hour, with first deliveries scheduled for early Q4 2019.
Loza Radar:
(www.lozaradarafrica.co.za and http://www.worldwidegeological.com.au/index.php/loza-radar/ )
Drilling on AST’s concession has been augmented with specialist low-frequency radar surveys which show the depths of the sandstone/quartzite contact.
Loza is the world’s most powerful Ground Penetrating Radar (GPR). It delivers unrivalled high resolution imaging of the earths sub-surface to depths of over 200m. A survey using Loza radar allows for fast, accurate and non-invasive geophysical based surface exploration, and delivers instant and clear images of the subsurface.
GPR is based on “stacking” a series of ultra-wide band electromagnetic pulse emissions that are sent directly into the subsurface. The Radar captures information about the different conductive properties of the lithology directly under the device. The radar records the conductive differences, and shows – in section view – a geophysical based interpretation of different lithological interfaces, layers or objects.
The Loza radar runs over a known point of reference, in AST’s case, the drill holes, in order to calibrate the radar image. The radar can then track the sandstone and quartzite interface, allowing for a wider drill grid. This enables the client to have a wider drill grid, with calibrated Loza survey lines running across the grid.
Loza’s average daily production in non-cleared terrain is between 2.5 km and 4 km per day allowing for large survey’s to be completed in a short time frame. Importantly the acquisition of data is environmentally friendly where clearing for survey lines is not necessary.
A professional geological survey has been completed, and a Leapfrog 3D model created using drill hole and radar data.