Threre is a small deposit of thundereggs at Bysta and
agates are typically gray to light blue sometimes with yellow tint and
few with banding features are found. That's all I know about those
thundereggs.
Click on the pictures to see larger and closer-up pictures.
Rough Appearance: Rough Appearance: Smooth bubbly surface on unweathered thundereggs.
A mix of yellow and bluish black colors on cut thunderegg shells are
dead giveaways.