Detecting Hematite-Rich Iron Ore in Magnetically Quiet Terrains

Using gravity to see what magnetometers miss

The Challenge

Exploration geologists often rely on magnetometry to identify iron ore targets—but what happens when the ore is invisible to magnetic sensors?

That’s the case with hematite-rich iron deposits, which lack the magnetic signature of magnetite. These non-magnetic bodies often appear as unexplained “gaps” in airborne or ground magnetic surveys. However despite being harder to detect, hematite is still a commercially viable source of iron, especially in weathered or oxidized terrains.

Conventional workflows risk leaving these resources hidden in plain sight.

Geological Context

Hematite (Fe₂O₃) forms through oxidation of magnetite and often appears in steeply dipping structures with density ranges around 3.5–3.6 g/cm³. These deposits frequently occur in structurally complex terrains where magnetic contrast is minimal.

Examples can be found in regions like the Pilbara Craton (Australia) and Carajás Province (Brazil). Research has shown the potential for gravity surveys but often the traditional cost and complexity of gravity surveying equipment has limited commercial use (learn more here)

Recommended Approach

High-resolution gravity surveys utilsing modern gravimeters are ideally suited for detecting hematite-rich iron ore due to their sensitivity to density variations. Using field portable gravimeters field teams can rapidly collect data across rugged or remote terrains where traditional tools struggle.

Where terrain limits ground access, the potential for near market drone-based gravity surveys presents a unique solution for large scale data acquisition whilst maintaining meaningful resolution vs traditional airborne gravimetry.

Gravity surveys in these applications are most effective when used in conjunction with:

·         Geological mapping to define structures

·         Hyperspectral imagery to identify iron oxides

·         Soil geochemistry or portable XRF to verify near-surface anomalies

Taking an integrated approach incorporating gravity surveys in haematite-rich iron ore provides better subsurface insight, sharper targeting, and higher confidence in exploration outcomes. This can lead to improved drill accuracy, revival of brownfield targets and improved orebody definitions and modelling.

Best Practices & Considerations

·         Use 50–100 m station spacing for near-surface target resolution

·         Apply terrain and drift corrections for data consistency

·         Model results in 3D and compare against drill logs if available

·         Combine with hyperspectral, soil geochemistry, or legacy magnetic data to contextualize gravity anomalies

·         Prioritize areas with structural control or known banded iron formation (BIF) alteration for the best response

Gravity alone doesn’t define mineralogy—but paired with other datasets, it becomes a powerful tool for discovering what magnetics alone cannot see.

How can SMG help?

SMG are passionate about changing the world of gravity measurements. We offer instrumentation, survey services and consultancy.  GAIA-FIELD is our flagship field-ready VBA MEMS Gravimeter;

·         Lightweight and robust design

·         microGal sensitivity with low drift and outstanding linearity in real conditions

·         Practical field deployment with self-levelling gimbal

Explore  further how our technology is changing gravity surveying.

If you would like to learn how SMG Gravity could improve your next exploration campaign please do Contact Us