Anza-Borrego Desert Paleontology Society
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Rocks of Anza-Borrego

The three primary minerals of granite shown here are mica (bright colors), feldspar (grey with parallel lines) and quartz (irregular grey at bottom).Pictured below are some of the rocks you might see on a hike in the Anza-Borrego Desert State Park.   

But these rocks have been cut into extremely thin sections not more than 10 microns thick and are viewed under the microscope.  

In many areas of geological study such as mineralogy, petrography, sedimentology and so on, thin section preparation is needed in order for samples to be examined microscopically for analysis of  the characteristics of the soil or rock. 

This analysis is normally carried out using transmitted polarised light which creates a need for thin sections of known and exact thickness. 

Thin sections


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Biotite Mica

Biotite mica is one of the most colorful minerals in thin section.

The biotite appears to be different colors, depending on the angle from which it is viewed
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Granite

The three primary minerals of granite shown here are mica (bright colors), feldspar (grey with parallel lines) and quartz (irregular grey at bottom).
Picture

Microfaults in Granite

Microfaults in granitic material 
from the Borrego Shear Zone 
about 1/3 of the way up 
Montezuma Grade

Photographs by Jimmy Smith, Anza-Borrego Desert Paleontology Society
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  • Home
  • Events
  • Learn
    • Contact
    • Anza-Borrego Story
    • Park Geology
    • What is a Fossil
    • Why Study Paleontology
    • How Old Are These Rocks
    • Collecting History
    • Ethics of Collecting
  • Explore
    • Tour the Visitor Center
    • Fossil Treasures
    • Paleoclimatology
    • Rocks of Anza-Borrego
  • Collections
    • Research Permits
  • About Us
    • Paleontology Society
    • Certification Program
    • Educational Support Committee
    • Press Room
  • Join
  • Support
  • Store
  • Links
  • Member Sign In