Non-Destructive 3D Mineral Identification Using Spectral Micro-CT

While SEM-EDS and automated mineralogy offer quick surface-based insights, they face several limitations:

• Lack of 3D Information

Grain size, sphericity, and internal distribution cannot be captured from a single plane.

• Undetected Trace Phases

Minerals may go unnoticed if they’re not intersected by the prepared section.

• Sampling Bias from Density Settling

In resin mounts, heavier minerals like galena or gold may sink during curing, distorting abundance data.

• Poor Phase Contrast in Conventional CT

Minerals with similar attenuation, like pyrite and chalcopyrite, are indistinguishable, limiting analysis.

These issues compromise both the accuracy and representativeness of mineralogical data used for resource evaluation.

The Benefits of Using Spectral Micro-CT

Resolve Overlapping Attenuation Profiles

Spectral CT differentiates minerals like pyrite and chalcopyrite using complete X-ray attenuation curves instead of averaged grey levels.

Quantify Low-Concentration Minerals in 3D

Assess volume fractions of gold, tantalite, scheelite, or galena inside entire core samples or grain mounts without destructive prep.

Correct Sampling Bias from Resin Mounting

Visualize particle density gradients across the sample and retrieve accurate mineral distributions regardless of settling.

Enable Elemental Detection Using K-Edge Imaging

Identify heavy elements like Pb, W, Ta, or Au based on their absorption edges in the X-ray spectrum.

TESCAN’s spectral CT workflow combines energy-resolved X-ray imaging with full-volume 3D acquisition to characterize ore materials both structurally and chemically.

Step-by-Step Workflow

• Sample Preparation: Load grain mounts, intact cores, or crushed rock fragments directly, without requiring polishing or embedding.

• Conventional CT Scan: Perform structural imaging to identify zones of interest and obtain overall mineral distribution patterns.

• Spectral CT Acquisition: Capture photon-resolved attenuation data using the PolyDet II detector over 140 energy bins.

• K-Edge and Zeff Mapping: Extract material-specific features from attenuation curves to identify and segment minerals with similar densities.

• Quantification and Visualization: Use TESCAN Spectral Suite and ORS Dragonfly to measure volume fractions, sphericity, and spatial orientation of target phases.

At the core of this workflow is TESCAN’s spectral micro-CT technology, which provides:

Sulfide Sample: Galena, Pyrite, Chalcopyrite

Spectral CT resolved galena using Pb K-edge contrast and distinguished between pyrite and chalcopyrite based on Zeff and density, while conventional CT could not.

Grain Mount: Tantalite, Scheelite, Cassiterite

Traditional resin mounts showed particle clustering and settling bias. Spectral CT corrected volume estimates and separated Ta- and W-bearing grains via K-edge imaging.

Core Sample: Gold Detection in Field Rock

A 5 cm core slice was analyzed for gold. Spectral CT positively identified 80 µm grains using gold’s 80.7 keV absorption edge—demonstrating the method’s ability to detect low-concentration, high-value phases even when partially obscured.

These examples highlight how spectral CT enables confident mineral discrimination across a wide range of geological applications.