What FACTS ABOUT ROCKS do you know? They are abundant on earth, and yet little is known about them. These facts will increase your knowledge of the rocks.

Large crystals found in geodes and other rocks are relatively rare. Pink ChalcedonyA ... and precious minerals such as emeralds—are the most common class of minerals, as well as the major ...

Hubbard, who first joined the USGS as a postdoc, is part of the agency’s Earth Mapping Resource Initiative (Earth MRI).