What type of rock or mineral is in this photo?

Question

http://i203.photobucket.com/albums/aa242/justask23/DSC00182.jpg

I found these rocks about a kilometer south of Anniversary Narrows which is a few miles north of Lake Meade in southern Nevada. Rocks are partially translucent and have very glassy and smooth surfaces with sharp corners. I think it might be a form of Agate but I'm not sure. 10pts for best answer. Thanks!

Answer 1

They look like chert, or flint

Answer 2

They look like geode's!!!!

Answer 3

Well what you have there is known as microcrystalline quartz. The specimens may be  petrified wood but this type of quartz is also known as chalcedony.