Scientific method
X-ray diffraction
Also known as XRD
Determines what crystalline phases are present, and their structural parameters, from the angles at which a sample diffracts X-rays. It identifies structure, not composition: two minerals of identical chemistry but different structure are distinguishable, and two of identical structure but different chemistry are not.
Classification
- method class
- experimental
- access
- indirect
How this record is known
- 2
- Settled consensus
- Cited as the accepted position of the discipline.
- 1
- Interpretation
- Reached by reasoning from evidence, or produced by a named model.
3 of 3 claims on this page cite at least one registered source. Counts describe how each statement is known, not how likely it is to be true.
What Lithoen records
Each claim states how it is known and cites its evidence.
EstablishedIt identifies structure, not composition: two minerals with the same chemistry but different structures are distinguishable, and two with the same structure but different chemistry are not. Amorphous material is invisible to it.
Quantifying mineralogy by X-ray diffraction is difficult where phases are highly weathered: the USGS soil survey records that reliable quantification must account not only for all crystalline phases but for poorly crystalline clay phases and amorphous material as well.
- precision note: Recorded so that a result from this method is never read as more than the method can support.
Evidence support: Supported by the cited evidence · one source
Evidence: Smith 2013 · Primary authority
EstablishedThe angles at which a crystalline sample diffracts x-rays.
X-ray diffraction records the angles at which a crystalline sample diffracts a monochromatic X-ray beam. The USGS laboratory manual describes the geometry: source and detector sit on a graduated circle centred on the powder specimen, the detector rotating through 2θ as the specimen rotates through θ, and copper targets radiating at about 1.5 angstroms are usual for geological work.
- precision note: What the instrument records and what a geologist concludes from it are different statements; this claim is about the former.
Evidence support: Supported by the cited evidence · one source
Evidence: L.J. 2001 · Primary authority
InferredWhich crystalline phases are present and their structural parameters.
Because each crystalline material has a characteristic atomic structure it diffracts X-rays in a unique characteristic pattern, so the method yields which crystalline phases are present. Where proportions are wanted, as in the USGS national soil survey, they are calculated by Rietveld refinement with an internal standard added so that the amorphous component can be estimated.
- method: The inferential step from instrument reading to geological information.
Evidence support: Supported by the cited evidence · 2 sources, multiple sources, independence unknown
Evidence: L.J. 2001 · Primary authority; Smith 2013 · Primary authority
In the knowledge graph
- X-ray diffraction provides evidence for Forsterite
- X-ray diffraction provides evidence for Quartz
Record last updated 2026-09-06. Corrections follow the published corrections policy; superseded claims are retained, never silently edited.