UCSB Science Line
Sponge Spicules Nerve Cells Galaxy Abalone Shell Nickel Succinate X-ray Lens Lupine
UCSB Science Line
Home
How it Works
Ask a Question
Search Topics
Webcasts
Our Scientists
Science Links
Contact Information
I am studying a polished cross-sectional piece of an igneous rock. How do I determine which phases/ compounds crystallize first (from the molten material) from the micro graphs taken?
Question Date: 2011-04-27
Answer 1:

Igneous rock is formed from the cooling of liquid magma or lava. There is a very straightforward relationship between crystal size and cooling time for igneous rocks: crystals that appear smaller in a micrograph came from lava which cooled more quickly (formed faster), while crystals that appear larger in a micrograph cooled more slowly (formed slower). If the rock does not appear to have any crystals, but instead looks smooth or glassy, that rock formed the most quickly- the lava cooling was so fast, that crystals did not even have time to form. In general, rocks with small crystals that formed quickly were probably formed on the earths surface where it is cooler, and conversely, rocks with larger crystals that formed more slowly were likely formed deeper in the earth, where it is warmer and the cooling time is longer.

Have a nice day!


Click Here to return to the search form.

University of California, Santa Barbara Materials Research Laboratory National Science Foundation
This program is co-sponsored by the National Science Foundation and UCSB School-University Partnerships
Copyright © 2017 The Regents of the University of California,
All Rights Reserved.
UCSB Terms of Use