Sunstones are bits of volcanic glass, clear to yellow in color. While they do have some value as a jemstone, it is unlikely that you will find a large enough sample out here. Take a while to look around and see what you can find. On a nice sunny day, the ground sparkles in places!
Note that this cache is on a private mining claim for the federal government, you can take away stones, but you need to regester in the white mailbox on the road leading in if you do so, and you can't re-sell any sunstones that you find.
I stole Huaso's link, so if you want more information on Sunstone Knoll, go Here Thank you, Huaso!
The are a few sunstones in the bag with the log book, please leave them there--I put them there so you could see what you are looking for.