Two old rocks

It is cold and it has been raining for much of the last 24 hours. A day to think of warmer times!
When on holiday I always bring back a local rock as a cheap memento. Here are two that I collected earlier.
The concretion of shells in the background is from Iceland. Most of Iceland is composed of volcanic rocks  but on the Tjörnes Peninsula there is a special place named Hallbjarnarstaðakambur where there are sedimentary deposits with huge layers  of fossilised seashells which are over 3 millions years old. 
The colourful rock in the foreground is from much nearer home, from Derbyshire. It is a small piece of Blue John  a form of fluorite with bands of a purple-blue or yellowish colour. In the UK it is found only at Blue John Cavern and Treak Cliff Cavern at Castleton in Derbyshire. During the 19th century, it was extensively mined for its ornamental value, and made into wide variety of ornamental items ranging from knife-handles to chalices. You can see a particularly spectacular pair of Blue John vases here.Mining continues today but only on a very small scale.