Red rocks, purple rocks, railways and reefs

Last day and back to Cabo de Gata – the northern end this time, but starting with a stop at Cala Cuerva that we had missed at the end of Day 4. The rocas rojos y violetas  are Cinto ignimbrite from the Rodalquilar caldera that have been hydrothermally altered to dramatic shades of violets and ochres that show to tremendous advantage in this foreshore setting.

However, before we looked at these we checked out the Messinian marine sediments on the southern side of the cala where we found puzzling ‘balls’ of concentric spheres of layered material – oncolites?
LATER... I've now found out that these are rodoliths/rhodoliths - balls created by red algae - see  http://en.wikipedia.org/wiki/Rhodolith . Thanks to Professor Paul Wright for that info on a trip to Blaen Onneu quarry!

Onward to the old mining town of Rodalquilar for coffee before going to have a look at the Casa de Los Volcanes where there is a truly excellent interpretative exhibition of the area’s geology. Unfortunately it was shut for the day as the curator was unwell so I’ll need to post the photos I took last summer of the explanation panels.
We had a damp lunch in Agua Amarga – I’d had unrealised visions of a relaxed ‘last lunch’ at a chiringuito by the beach bathed in spring sunshine but it piddled down so not as relaxing as planned. The headland above the village is a fascinating archaeological site – the seaward end of the mineral line from Lucaiñena and a look around revealed scraps of ore on the ground which we identified as magnetite by their cubic habit and ability to attract compass needles.
Final stops were on Mesa Roldan and the beach to the north to examine the relationships between dacite volcanic domes and reef facies and we wound our way back to Turre over the Sierra Cabrera past the stops from Day 3.