Terrain Minerals Finds Conventional Processing Pathway for Lightning Gold

Conventional Flowsheet Clears Lightning’s First Processing Test

Terrain Minerals Limited (ASX:TMX) has cleared one of the more consequential early hurdles for its Lightning Gold Project, with first-pass testwork indicating the mineralisation can be treated through a standard gravity and cyanide leach circuit. Optimised overall gold recoveries reached 87.0%, 92.1% and 93.7% across three composites, with no refractory or preg-robbing behaviour identified.

The result matters because Lightning does not appear to require roasting, pressure oxidation, bio-leaching or ultra-fine grinding - processing routes that can add substantial capital and operating complexity. The tests delivered their headline results at a conventional P80 75-micron grind, a particle size used across many Western Australian gold plants.

Gravity Recovery and Reagent Changes Lift Results

Gravity recoveries ranged from 30.6% to 50.8% using a Knelson concentrator before cyanide leaching. Composite 3 produced the strongest response, with 50.8% of its gold recovered through gravity and 93.7% overall recovery under the best 48-hour conditions.

Composite 1 was the weaker performer under baseline conditions, returning 75.4% recovery at the standard grind and reagent regime. That figure rose to 87.0% after increased cyanide dosage, potentiometric titration control and the addition of 100 grams per tonne of lead nitrate. Terrain said these are routine adjustments in operating gold plants, rather than specialised treatment requirements.

The release also points to generally rapid leach kinetics, reporting optimised 24-hour recoveries of 82.1%, 91.7% and 95.3% for Composites 1, 2 and 3 respectively. However, the announcement’s tables contain a discrepancy for Composite 3: the 24-hour table reports 95.3%, while its 48-hour optimised summary reports 93.6%, below the headline 93.7% result. The company does not explain the difference in the release, leaving the underlying test-by-test data important for later study work.

RC Samples Leave Core and Variability Questions Open

The results are encouraging, but they are not yet a project-level processing design. Independent Metallurgical Operations tested 18 bottle-roll leach tests across three composites prepared from previously collected reverse-circulation chip samples. Terrain cautioned that RC material may have a finer size distribution than diamond core, potentially affecting the gravity recovery results.

That limitation is material. Bottle-roll tests also use laboratory mixing and residence conditions that may be more favourable than a commercial plant, while the three composites cannot establish metallurgical variability across the deposit. Terrain plans diamond drilling for confirmatory gravity and cyanide leach work, further reagent optimisation and broader variability testing before advancing towards a future scoping study. The company also stresses that the testwork is not a Mineral Resource or Ore Reserve estimate and does not establish economic viability.