📊 Pebbles have traditionally been treated as an unavoidable part of grinding circuits. A new joint analysis by SRK Consulting and TOMRA Mining argues that not all of them should be processed.

In many hard-rock mining operations, pebbles account for 5% to 30% of mill feed. These coarse, hard particles are typically crushed and recirculated, consuming additional energy, occupying mill capacity and increasing wear on grinding and crushing equipment.

According to the study, pebble streams are far from homogeneous. While some particles contain high concentrations of valuable minerals, others carry little or no economic value.

💬 "A significant portion of the contained metal can be concentrated within a smaller fraction of the mass, with up to 80% of the metal found in around half of the particles," said Adrian Dance, Principal Consultant at SRK Consulting Canada. "Selective processing of pebble streams has been shown to increase both feed grade and throughput, reinforcing the economic potential of this approach."

⚙️ The proposed solution uses X-ray Transmission (XRT) sensor-based sorting, which analyses each particle according to its atomic density before separating valuable ore from barren rock. Pebble streams are particularly well suited to this application because they are already screened, washed and conveyed before sorting.

💬 "Rather than treating the material as a bulk flow, this particle-by-particle approach allows operations to retain value while rejecting material that would otherwise add cost without contributing to recovery," said Fernando Romero-Lage, Area Sales Manager at TOMRA Mining.

📈 According to the companies, documented copper operations have achieved up to a 6% increase in plant throughput using selective pebble processing. At one Canadian mine, throughput gains translated into an estimated US$21 million in additional annual revenue, while another operation in Peru reported multi-million-dollar benefits through higher feed grades and increased throughput.

The findings reflect a broader shift in mineral processing - from treating pebble streams as an unavoidable by-product to managing them as a recoverable resource. Rather than processing every tonne, sensor-based sorting enables operators to process only the material that creates value.