Solids & materials analysis · XRD reference

Clay speciation by X‑ray diffraction

A working reference for how XRD identifies crystalline solids, why clay fractions are run as oriented mounts, and how ethylene glycol treatment separates expandable smectitic clays from non‑expanding species like illite and kaolinite.

8 panels Bragg’s law Oriented clay mounts Glycolation

Infographic: X-Ray Diffraction (XRD). Eight panels covering what XRD measures in solids, how the instrument works with Bragg's law, reading a diffractogram, bulk powder versus oriented clay mounts, why glycolation is used, the clay speciation workflow, common clay mineral signatures for smectite, illite, kaolinite, chlorite, and mixed-layer illite/smectite, and key takeaways. — Reference sheet — XRD clay mineral speciation

Where this fits

XRD is our flagship solids capability, paired with FTIR under Solids & Materials Analysis. Clay speciation and glycolation are the specific differentiator: we don’t just identify a bulk mineral list, we distinguish expandable smectitic clays from fixed, non‑expanding species.

Reading the signatures

Smectite shifts from ~12–15 Å to ~17 Å after glycolation. Illite, kaolinite, and chlorite hold their basal spacing. Mixed‑layer illite/smectite shows a broad, partially‑shifting composite peak.

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