These small agates from north Dakota are very similar to some of the Gobi agates from China. In the past very nice ones with good detail like this one were common but in recent years the price of good ones first skyrocketed to hundreds of dollars a piece and then they vanished to be replaced with very poor quality versions. I was very happy when the Gobi agates provided an alternative to these wonderful little agates. 20mm with a 2.5 mm hole.