This really cool rock we found comes from a stretch of river that leads out to the sea down in South Ayrshire. It is cool because it looks like mossy red jasper slash chalcedony on the bottom. 
This crystal from Scotland probably started life as a whole nodule with the red jasper material forming the skin. Inside there would be a layer of quartz which makes a lovely defined line where it meets the other minerals. Next is a layer of red mineral, likely carnelian judging by the shine. After that comes another layer of quartz in the centre.
It is refreshing to see chunks of agate nodule like this. We see a lot more small, bubble like agates. This one has been around for a long time.