What do rocks tell us?
Every rock has a story to tell. Geologists study the microscopic world of
rocks in order to better understand the earth's history. This type of rock
exploration follows a logical sequence.
The first step is to identify the minerals that compose the rock. Minerals can be
difficult to identify with the naked eye, but they have characteristic optical
properties that are easily distinguished under the microscope. Some of these
properties are color, cleavage and twinning.
The next step is to describe the architecture of the rock. The arrangement of
grains, the abundance of different minerals, the structures within those minerals
all aid in determining which processes were important in the formation of a
particular rock. Sedimentation, crystallization, deformation, and metamorphism
are processes that leave their signatures in rocks. Certain signatures can be
read only with the microscope.
Finally, geologists use the clues they gather to solve the puzzle and make an
interpretation of the rock's history. The facts may support more than one
interpretation, but geologists narrow the possibilities with each advance in their
understanding of rock processes.
Make your own interpretation of a rocks history.