This lot is for the photographed handful of Chalcedony Pebbles. We regularly find these on agate hunting expeditions in Ayrshire. These are known locally as diakethyst and might include tiny agates.
They are a mix of colours, including purple, pink, red, white, and grey. They are all less than a cm across or only slightly larger.
These are formed by bubbles of other minerals rising through cooling lava. Larger bubbles form agate, Chalcedony, and quartz pockets. These bubbles were too small.
You can learn more about diakethyst and agate on our blog.