Trancas Geodes from Mexico. These geodes have a darker gray and tan exterior with a translucent to light blue interior. They can have a variety of crystal shapes inside, including fine druzy, large crystals, needle-like crystals, or they can be almost solidly filled with chalcedony.
Some can fluoresce green under short wave UV light due to trace uranium content.
Size can range from a few inches to fist size, usually 2 pieces per pound.