What's Inside These Rocks?

Jessi and Squeaks have some cool rocks. What do you think is inside them?
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SOURCES:

http://www.sciencebuddies.org/science-fair-projects/project_ideas/Geo_p042.shtml#background
http://science.jrank.org/pages/3007/Geode.html
http://www.ducksters.com/science/earth_science/minerals.php
http://www.mineralogy4kids.org/all-about-crystals