We just finished a batch of tumbling which included a few small chalcedony pebbles and agate pieces. These are collected from around Scotland and taken home where we wash and tumble them to a nice shine.
This Ayrshire Chalcedony pebble was found near Alloway last year. It has a lovely purple hue to it with a reddish tone. If you cut it in half there may be agate material in the centre. It looks like there is a bubble in it.