These agates are from Minnesota where I have not lived for over 50 years but still visit family regularly. I am not sure how long I have been carrying them with us as we moved but I decided to do something with them by taking this photo and another also uploaded today with just a few of them. They were polished in a rock tumbler.
Agate is a cryptocrystalline variety of silica, chiefly chalcedony, characterised by its fineness of grain and brightness of color. Although agates may be found in various kinds of rock, they are classically associated with volcanic rocks and can be common in certain metamorphic rocks. [wikipedia]