Quantitative modal analysis is used to determine the volumetric proportions of the minerals that make up the rock, determined by areal analysis of a thin section. Point-counting is a technique utilized by our geologist petrographers to get an approximate modal composition of the rock. A systematic selection of 300 – 500 points on a thin section are described and record exactly as observed at each point. These points are compiled together to determine the rock composition.

Petrographic Categories Observed Interests:

  • Mineralogy
  • Morphology
  • Diagenetic Relationships
  • Clay Types
  • Carbonate Microfacies
  • Pore Types
  • Rock Fabric

Precimat utilizes specialized computer software and an automated stepper stage mounted on our polarizing microscope to perform point counting on any type of thin section.

We can count up to 61 mineral species per sample and offer customizable species options to best fit your petrographic needs. We can accept oversized slides up to 66mm by 90mm with a possible analysis area of 66mm by 50mm.

Modal analysis can be simplified in conjunction with our thin section feldspar staining option which helps the user visually distinguish the subtle differences between alkali feldspar, plagioclase, and quartz by selective staining (Bailey and Stevens, 1960).

Users of petrographic modal analysis:

  • Igneous and Metamorphic Petrologist
  • Exploration Geologist
  • Sedimentologist
  • Volcanologist
  • Archaeologist
  • Micro-paleontologist
  • Ceramic Engineers
  • Petrophysicist

Bailey, E.H. and Stevens, R.E., 1960.Selective staining of K-feldspar and plagioclase on rock slabs and thin sections. Am. Mineral. 45:1020-1025.