Sensor-based sorting lets miners reject barren rock before it's ever crushed, saving energy, water, and tailings volume at industrial scale.
Polymetallic deposits, the orebodies that carry multiple economically valuable metals in a single rock, present a distinctive processing challenge: the valuable minerals are locked together with each other and with vast volumes of barren rock, demanding both heavy grinding and complex multi-stage separation. That complexity is one reason polymetallic operations have become early adopters of sensor-based pre-concentration. The traditional fix is to grind all of it to powder and let chemistry sort it out, a step that consumes around 53% of a typical mine's total energy.
A quieter technology is rewriting that math: X-Ray Transmission (XRT) sorting. It reads the density of every rock on the belt in milliseconds and ejects the barren ones before they ever reach the mill.
What XRT Actually Does
As ore moves across a high-speed belt, X-rays penetrate each particle and a detector reads the rock's internal density in milliseconds. Dense, metal-bearing rocks are flagged. High-pressure air jets eject the barren ones into a separate waste stream before they ever reach the energy-intensive wet plant. The technology is supplied by several competing vendors including TOMRA, Comex, Steinert, and Redwave, and an independent peer-reviewed economic analysis published in MDPI's Minerals found that XRT sorting can reduce capital and operating costs by up to 20%.
Two material streams come out instead of one: a smaller, richer feed for the mill, and a clean, dry waste stream that bypasses grinding, water, and tailings dams entirely. The energy logic follows directly from the mass logic. Every tonne of barren rock rejected before the mill is a tonne that never gets ground.
Independent Test Results
Academic research is now catching up with vendor claims. A 2026 peer-reviewed study published in MDPI's Sensors journal tested low-grade European copper ore from the Złote Hory mine in the Czech Republic using a dual-energy XRT laboratory sorter. The study reported 95.67% copper recovery in 52% of the original mass, with the waste stream falling to just 0.04% copper. The pre-concentrate grade was 1.82× the feed grade. Critically, the study was not commissioned by a sorting vendor.
The same line of academic work has extended to gold, lithium spodumene, and complex sulphide ores, with researchers increasingly combining XRT with other sensor modalities and machine vision to handle ore types that were previously considered unsortable.
Polymetallic Operations Already Using It
Manaila, Romania. Vast Resources' Cu-Pb-Zn polymetallic sulphide mine ran a feasibility study with XRT pre-concentration. International Mining reports test results for the mine's typical disseminated-to-massive sulphide ore: 93.1% of copper, 82.2% of lead, and 92.4% of zinc recovered in just 45% of the original mass. More than half the rock could be rejected before milling while retaining the great majority of payable metal.
Clayton Silver Mine, Idaho. CMX Gold & Silver tested XRT on a one-million-tonne historical Ag-Pb-Zn stockpile. Published test results show the sorter recovered more than 70% of the stockpile's metals in just 10% of the original mass, upgrading the silver grade by 6.4× and the lead and zinc grades by 7×.
Kutcho, Canada. Kutcho Copper's Cu-Zn-Ag-Au project tested XRT on bulk samples from its Main and Esso deposits. International Mining reports the test work rejected 13% of run-of-mine material before milling while recovering approximately 99% of the copper, zinc, silver and gold reporting to the sorter, a smaller mass cut, but near-zero metal loss.
The Bottom Line
Polymetallic processing has historically been an exercise in grinding everything and chemically sorting what's left. Sensor-based sorting flips the sequence: physically sort what you can, then grind what's worth grinding. With falling grades and rising energy bills, the question for operators is shifting from whether sensor-based sorting belongs in their plant to which sensor, and at what cut-point. The complexity of polymetallic ore, long a constraint, is becoming the proving ground for cleaner mining.
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