SELECTIVE GYPSUM MINING – PENONG (SA)

Client: GRA Gypsum Resources Australia
Location: Penong, SA
Project Start Date: June 2025

 

​Challenges

The gypsum deposit at the Penong site features two distinct geological layers:

• The top layer consists of soft gypsum that can be easily stockpiled using dozers and requires minimal further processing.

• Beneath this lies a much harder crystalline gypsum, known as selenite, located just above the water table.

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Historically, GRA used a 250 ton mining excavator to free-dig this selenite. However, this approach presented several key issues:

• The material was extracted in large, uneven lumps, necessitatingfurther processing through an impact crusher meet product specification.

• Excavating near the water table exposed the selenite to saltwater, which significantly increased leach times and delayed product delivery.

• Drilling and blasting were not considered viable due to operational risks, environmental concerns, and high costs.

• While effective in some areas, the 250 ton mining excavator proved inefficient in harder zones near the water table.

 

Solution

To address these challenges, we deployed the Tesmec 1150 RH surface miner for selective mining of the selenite layer.

This approach provided key advantages:

• Precise and efficient extraction of hard crystalline gypsum.

• Minimized contact with the water table, reducing saltwater exposure.

• Significantly reduced need for secondary crushing.

• A more controlled, consistent, and safer mining process.

 

​Result:

The deployment of the Tesmec 1150 RH at Penong delivered significant operational and commercial benefits:

• Reduction in use of the 250 ton mining excavator, decreasing reliance on heavy, high-consumption equipment.

• Ability to selectively mine a thin layer of high-purity gypsum located just above the water table, with minimal exposure to saltwater, preserving material integrity.

• Approximately 50% reduction in leach time, enabling faster turnaround and earlier product availability.

• Crushing reduced by 95%, as approximately 95% of the milled material from the 1150 RH meets specification without further processing.

• Process streamlining, reducing the original 7-step operation to 6 steps, resulting in a more efficient and less equipment-intensive workflow.

• Faster time-to-market, with halved leach times translating into approximately 50% quicker delivery to customers.

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Key facts:

• Efficient option for selectively mining thin layer of material on top of ore body

• Ability to mine shallow hard material with increased efficiency

• Reduction in leach times enables product to go to market faster

• Significantly reduced crushing cost by producing a uniform particle size with 1150 RH

• Trialled and demonstrated 1150 RH which delivered the production rates suited to their needs