Electric Blue Agate

What a stunning yet unique design this is by our favourite designer, Nature.

It is a good example of an agate formation with the concentric waves, but the subtle blue-grey colour is most likely due to traces of titanium in the original silica-rich gel. 

That almost certainly happened in this way only once, so it really is unique, and the mineral sample was found in Britain too.

And the grey and blue hues make it so delicately evocative when printed on to the finest Chinese silk.