Visual logs are on-site geological descriptions of drill core or chips recorded as drilling progresses. When visible mineralisation is present, the geologist estimates the percentage of ore minerals observable in the core or chips — a process called visual logging.
Assay results are the definitive measure, but they take weeks to return from the laboratory. Visual estimates provide an early indicator of grade while investors and geologists wait for confirmation. They appear in company announcements as qualitative descriptions or percentage estimates of mineralisation.
| Mineral | Distribution | Commodity | Visual Estimate | Estimated Grade |
|---|---|---|---|---|
| Lithium | |
|||
| Spodumene | 8% | Lithium (Li2O) | 0% | |
| Lepidolite | 7.70% | Lithium (Li2O) | 0% | |
| Amblygonite | 8.40% | Lithium (Li2O) | 0% | |
| Petalite | 4.50% | Lithium (Li2O) | 0% | |
| Zinnwaldite | 1.60% | Lithium (Li2O) | 0% | |
| Nickel | |
|||
| Pentlandite | 34.20% | Nickel Sulphide | 0% | |
| Millerite | 64.70% | Nickel Sulphide | 0% | |
| Nickeline | 43.90% | Nickel Arsenide | 0% | |
| Niccolite | 43.90% | Nickel Arsenide | 0% | |
| Violarite | 38.90% | Nickel Sulphide | 0% | |
| Copper | |
|||
| Chalcopyrite | 34.60% | Copper | 0% | |
| Cuprite | 88.80% | Copper | 0% | |
| Chalcocite | 79.80% | Copper | 0% | |
| Covellite | 66.50% | Copper | 0% | |
| Bornite | 63.30% | Copper | 0% | |
| Malachite | 57.70% | Copper | 0% | |
| Azurite | 55.10% | Copper | 0% | |
| Other | |
|||
| Cobaltite | 25.00% | Cobalt | 0% | |
| Tetrahedrite | 30.00% | Antinomy | 0% | |
| Argentite | 87.00% | Silver | 0% | |
| Molybdenite | 59.90% | Molybdenum | 0% | |
| Sphalerite | 60.00% | Zinc | 0% | |
| Galena | 87.00% | Lead | 0% | |
Find the mineral
Locate the ore mineral for your commodity in the table. Supported minerals include spodumene, lepidolite, and others for lithium; pentlandite and millerite for nickel; plus additional commodities in the full tool.
Enter the visual estimate
Input the percentage of that mineral visually observed in the core or chips.
Read the estimated grade
The calculator applies the mineral's distribution factor to return an estimated grade for the relevant commodity.
The distribution factor reflects how much of a commodity is contained within a specific ore mineral. For example, spodumene contains approximately 8% Li2O by weight. If a geologist estimates 10% spodumene in the core, the Visual Logs Estimator returns an estimated Li2O grade of approximately 0.8%.
Different minerals within the same commodity carry different distribution factors. Spodumene and lepidolite are both lithium-bearing minerals, but their Li2O content differs significantly. The estimator accounts for this.
Once you have an estimated grade, compare it against the commodity thresholds in our commodities grade guide to understand whether the visual result suggests low, medium, or high grade mineralisation.
Have a grade estimate and want to size the ore body? Run it through the Resource Calculator to get a back-of-envelope tonnage and contained metal figure. Or use the Residual Grade Calculator if you need to strip out a high-grade core from a wider intersection.
A visual log is an on-site geological description of drill core or chips, recorded by a geologist at the drill rig. It includes observations on mineralisation, rock type, structure, alteration, and any visible ore minerals.
Accuracy varies by commodity and mineral. Some minerals such as spodumene are more visually distinctive and yield more reliable estimates. Others are difficult to distinguish visually. Treat all visual estimates as indicative only — laboratory assays are the definitive measure.
The distribution factor is the proportion of a commodity contained within a specific ore mineral, expressed as a percentage. It converts a visual mineral estimate into an approximate commodity grade.
No. Visual estimates are not audited, not JORC-compliant, and can differ materially from final assay results. They are useful for early orientation only. Always wait for laboratory confirmation before drawing conclusions.
The tool covers lithium minerals (spodumene, lepidolite, amblygonite, petalite, zinnwaldite), nickel minerals (pentlandite, millerite), and additional commodities listed in the full tool.
