Polarised light microscopy (PLM)
Definition
A microscopy technique in which polarised light is passed through a thin section or grain mount, revealing optical properties (birefringence, extinction angle, pleochroism) that allow mineral identification. One of the core analytical tools in forensic geology since Walter McCrone's era.
Related terms
- Comparative mineralogy
- The systematic comparison of mineral assemblages from a questioned sample and a reference sample to assess whether they share the same geographic...
- Forensic geology
- The application of geological sciences to legal and investigative problems, treating earth materials such as soil, rock, mineral, sediment, and dust as...
- Geo-provenance
- The determination of geographic origin of a geological material based on its physical, mineralogical, or geochemical characteristics. The same concept that geologists...
- Heavy-mineral suite
- The assemblage of high-specific-gravity minerals (greater than about 2.85 g/cm3) present in a sediment sample, typically including zircon, tourmaline, garnet, and hornblende....
- Trace evidence
- Small quantities of material transferred between people, objects, and locations during contact. Forensic geology focuses on the geological subset of trace evidence:...
Explained in
- History and Pioneers of Forensic GeologyA microscopy technique in which polarised light is passed through a thin section or grain mount, revealing optical properties (birefringence, extinction angle,...