Oriented Mount
Definition
A clay sample preparation in which fine clay particles are settled onto a glass slide so that their flat basal planes align parallel to the surface. This concentrates the basal reflections of clay minerals and enhances the diagnostic 001 peaks used for clay identification.
- Sample type
- Fine clay particles on a glass slide
- Alignment
- Basal planes parallel to slide surface
- Enhances
- 001 basal reflections in XRD
- Purpose
- Clay mineral identification
Common questions
Why must clay particles be oriented rather than randomly packed for this XRD analysis?+
Clay minerals are platy, and their most diagnostic reflections come from the repeating basal spacing between sheets. Settling particles flat onto a slide aligns those basal planes with the diffraction geometry and strongly enhances the 001 series of peaks that random powder packing would leave weak and hard to distinguish.
What does an oriented mount reveal that a random powder mount does not?+
It resolves closely related clay species such as illite, kaolinite, and smectite that would otherwise overlap in a random powder pattern, and combined with glycolation or heat treatment it lets an analyst track how basal spacing shifts, which is often decisive for identifying the specific clay mineral in a soil or trace evidence comparison.
Related terms
- Basal Reflection
- The diffraction peak arising from the repeat distance along the stacking direction of clay layer silicates (the c-axis or 001 reflection). Its...
- Bragg's Law
- nλ = 2d sin(θ). A monochromatic X-ray beam diffracted off the parallel lattice planes of a crystal produces constructive interference only at...
- D-Spacing
- The perpendicular distance between adjacent parallel planes of atoms in a crystal lattice, measured in angstroms or nanometres. Each set of planes...
- Mixed-Layer Clay
- A clay mineral in which two different layer types (for example smectite and illite layers) are interstratified in a regular or random...
- Rietveld Refinement
- A full-pattern fitting method for XRD quantification that models the entire diffractogram using crystal structure data for each phase, adjusting phase abundances...