This is a semiprecious type of chalcedony, agate is a microcrystalline variety of quartz. It is made by a series of processes that happen in cavities within solidified lava. Most agate you'll see is banded & can be any color in the spectrum.
 
This pendant was handmade here in Chico,CA by @gypsybomb. It is hung on a waxed cord.
 
Metaphysically, agate provides one with the feeling of security. It can also improve a persons concentration as well as calm an individual. 
 
Length: 14 inches
Width: 3"
Weight: 51 grams