Mineral Assay Lab Robot: Fire Assay to ABB Cells

Every gold or copper mine runs on numbers from its assay lab. Drill core and blast hole samples arrive by the bag, and the lab has to crush, split, weigh and test them fast enough for geologists and mill operators to act on the results. That makes the mineral assay lab robot one of the less visible machines in mining, and one of the busiest. This post goes from fire assay done by hand with crucibles and tongs, through the first automated sample preparation lines, to the robotic and X-ray labs of 2026, and looks at where ABB robots could fit.

An assayer uses long tongs to work crucibles in a glowing fire assay furnace, 2022. Photo: SoporteMinares / Wikimedia Commons (CC BY-SA 4.0)

How assayers tested ore with fire and tongs

Fire assay is centuries old. Georgius Agricola described assaying in De re metallica in 1556, and modern labs still use the same chemistry. Crushed ore is mixed with fluxes, a carbon source and powdered lead oxide called litharge, then heated in a crucible to between 1,000 and 1,200 °C. The lead collects the gold and silver and sinks to form a button under a glassy slag. Printed manuals with woodcuts of assay furnaces carried the method from one European mining town to the next.

A 1598 woodcut of ore testing and furnaces in an assay laboratory. Photo: Library of Congress via Wikimedia Commons (public domain)

Cupellation comes next. The lead button goes into a porous cupel of bone ash or magnesium oxide and is heated in air at about 1,000 °C. The lead oxidises and soaks into the cupel, leaving a tiny bead of precious metal, the prill, which the assayer weighs. Mine assay offices, such as the one from California's Empire Mine that is now kept in a museum near Grass Valley, were small rooms full of furnaces, balances and bottles. Every step meant lifting hot crucibles with tongs and working near lead fumes.

The Empire Mine assay office, now on display at the North Star Mine museum near Grass Valley, California. Photo: Jim Heaphy / Wikimedia Commons (CC BY-SA 4.0)

Labs got faster by running many samples at once, and a lab with several furnaces can process several hundred analyses a day. Mints checked bullion on precision balances, as in the San Francisco Mint's assaying division. Over the twentieth century, automation went mostly into moving material and taking the final measurement, while the chemistry stayed the same. Sample preparation machines came first, with crushers, pulverisers and splitters, and robot cells followed. Scott Automation, which owns the New Zealand brand Rocklabs, built a system for Peñoles in Mexico with separate robot cells for crushing, pulverising, flux dosing and fire assay.

The assaying division of the San Francisco Mint, with tables and assay scales for checking bullion. Photo: US National Archives via Wikimedia Commons (public domain)

Robots and X-rays in the assay lab today

The most talked-about change in gold assaying in 2026 is a method that skips the fire. PhotonAssay, developed by Australia's CSIRO and sold by Chrysos, hits a jar of about 500 grams of crushed sample with high-energy X-rays from a linear accelerator and reads the signal from excited gold atoms in about two minutes. Fire assay takes a 50 gram sub-sample through hours of fluxing and smelting. Chrysos reported FY26 revenue up 33 percent to A$88.1 million, 11.3 million samples processed and a contracted fleet of 87 units, and in October analysts were weighing its FY27 target of A$108 to 118 million.

Drill core laid out in labelled wooden boxes, here from Finland's Onkalo site, the form most exploration samples take before the lab. Photo: kallerna / Wikimedia Commons (CC BY-SA 4.0)

Someone or something still has to fill, label, move and store the jars, and the crushers still need feeding, so robots stay busy around the new instruments. Intertek offers robotic sample systems for minerals testing, from single cells to full lines, and says they cut heavy lifting and keep staff away from hazardous materials. Commercial labs such as Canada's Paragon Advanced Labs are adding PhotonAssay capacity as well. Where a lab keeps the classic method, a robot cell like the fire assay cell at Peñoles can take over the furnace work that assayers once did with tongs.

Ceramic vessels used for assays and refining precious metals. Photo: LukaszKatlewa / Wikimedia Commons (CC BY 4.0)

We found no ABB robot named in a mining assay lab, although ABB arms already do similar work in other labs and hot plants. At the SLAS 2025 lab automation show, ABB showed GoFa CRB 15000 cobots tending lab instruments and preparing samples. The IRB 1300 comes in a Foundry Plus version sealed against dust and water, which suits crushing rooms. ABB robots also work beside melting furnaces in foundries, which is close to the job of loading assay furnaces. Our post on the cement plant lab shows a similar sample line in another industry.

An ABB GoFa cobot working with lab instruments at the SLAS lab automation conference. Photo: ABB

Where robotic assay labs go next

Mines want results while the drill rig is still on site, so more assay work is moving next to the pit. PhotonAssay units are already going in at mine sites, for example the unit Firefinch and MSALABS were commissioning at the Morila project in Mali. Robotic preparation cells could follow them into the field, run around the clock and feed results straight into the mine's grade control, so geologists wait less for each hole. For homes the effect is indirect: cheaper and cleaner assaying is part of how metals reach batteries, wiring and jewellery.

An ABB IRB 1300 with Foundry Plus 2 protection, built to handle water and dust. Photo: ABB

No ABB assay project has been announced, so what follows is a possibility. A GoFa or IRB 1300 could weigh and dose samples, larger arms could move crucibles at furnace doors, and Flexley Mover AMRs could carry sample trays between the crushing room, the analysers and storage. SafeMove can keep people and robots apart in shared rooms. Cells like these are normally laid out and tested in simulation before anything is bolted down, which is where RobotStudio comes in.

An ABB robot beside a melting furnace in the aluminium casting shop of Hermeta in Asperen, the Netherlands. Photo: ABB

The open problems are practical. Rock dust wears seals and grippers, sample bags come in every shape, and hot crucibles are heavy, so cells need rugged tooling and regular maintenance. Cost is hard to justify for small labs that process a few hundred samples a day, and PhotonAssay changes which steps need automating in the first place. Labs also need people who can program and service robots as well as run the chemistry. Lead exposure and furnace heat are still the strongest reasons to take people's hands out of fire assay wherever a machine can do the job.

An ABB Flexley Mover P603 carrying crates. Photo: ABB

Innovation

AI solutions for effortless ABB robot control.

Automation

Robotics

ceojohntran@chatwithrobot.net

+84905311611

© 2025. All rights reserved.

qtran1215@gmail.com