Exploring Rocks: What Are Thin Sections
Ultrathin slices of rock mounted on glass slides are called thin
sections. Standard thin sections are 30 microns (0.03 millimeters) thick,
only slightly thicker than the 1 mil plastic film found in sandwich bags and
plastic wrap. The optical properties of minerals -- what you see when you
look through the microscope -- vary with the thickness of the mineral
slice. Quality thin sections have a uniform thickness of 30 microns. This
standardization makes it possible for geologists to recognize minerals as
they appear through the microscope.
A polarizing microscope, a thin section and an observant eye are the
only tools required to enter the microscopic world of rocks.
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