Assaying, Microscopy, Mineralogy & XRF/XRD

Assaying, Microscopy, Mineralogy & XRF/XRD

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SEM-MLA vs Optical microscopy (1 reply)

Millza79
5 years ago
Millza79 5 years ago

All,

 

Can anyone please let me know the pros or cons for the following methods on a polished thin section taken from a section of drill core:

 

SEM-MLA

vs Optical microscopy

 

Thanks

 

d
David
4 years ago
David 4 years ago
Like

MLA - SEM

Pro’s

  • Identification of gangue minerals based on chemical content (XRF) and back scatter.
  • Generally very accurate identification of sulphide minerals.
  • Automated methods to identify sparse mineral phases
  • Can assess spot chemical analysis (XRF).
  • When using the same potocols you get consistent identification.

Cons

  • Usually more expensive, more complicated slide preparation and longer turnaround.
  • Requires a highly trained and skilled technician to calibrate the machine.  The outcome is highly dependent on the technician and machine “SIP”
  • Carbon coated samples don’t allow for good colour photo micrographs, only SEM backscatter images available. No transmitted light photos.
  • Requires assaying for QAQC and verification the analyses are correct.  This does not always happen, and incorrect information can be assumed correct because a machine did the analysis.
  • Some mineral phases “polymorphs” not well identified.  These are samples with the same chemical composition but different crystal structure.  (i.e Coal, Organic carbon, diamond)

Optical Point Counting

Pros

  • Generally faster and more cost effective.
  • Best format for photomicrographs.
  • Skilled technicians can identify most sulphide and metallic oxide minerals. 

Cons

  • Most gangue or translucent minerals difficult to identify.  Only reflective minerals are identified.
  • Requires a skilled technician to conduct the analysis.
  • Qualitative data output, unless strict point counting modal procedures followed.
  • Identification of minerals dependent on technician, different outcomes or data can be generated by different technicians

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