PEÑA del HIERRO MINE
WHAT IS IT, AND WHAT CAN I EXPECT TO SEE?
This is the mine which is open to visitors. It is10 km from Minas de Rio Tinto village - you drive in convoy leaving from the mining museum, following your guide in his vehicle (it's too complicated to explain on a map).
First used by the Romans for silver and sulphur, the part you visit consists of a 200-metre tunnel (mining gallery) called Santa Maria, which you walk along (wearing a hard hat, provided). You can see shafts and galleries where the ores were extracted, an emergency exit in case the lift wasn't working, and chimneys where the steam from the locomotives used to transport minerals escaped. The ceiling is reinforced by beams of eucalyptus and pine (these particular types of wood and very flexible, and creak when they're about to break, warning the miners before the tunnel collapses).
The tunnel comes out on a balcony overlooking a small lake. The 25m-deep lake is, in fact, the crater of the mine, created by the Romans. Along the walls of the crater you can see layers of various colours - yellow, gold, white, grey - where the different mineral ores can be found - mainly used in the production of copper, but also silver and gold.
You can also see the remains of equipment and buildings used to wash, sort and process the minerals mined here, most recently to produce copper, sulphur, iron and lead, before they were loaded onto trains and sent either Huelva, to be exported by ship. The wooden lifts used to extract the minerals are 125 metres deep - the vertical mine was divided into 12 levels. Don't touch the pretty, clear stream of water which flows near the entrance to the mining gallery, as this water is highly acidic and will burn.
This is also where NASA's Astrobiological Institute is carrying out research, jointly with Madrid University, into the area's microbial life. The bare moonscape of the zone is very similar to that of Mars, both having conditions extremely inhospitable for living beings. While Rio Tinto is a "dead river" due to the lack of flora and fauna - plants, fish or frogs wouldn't survive the acidity of the water (2.2pH) - it does have micro-organisms which are able to prosper, many of which were previously unknown life forms. So the project, known formally as MARTE (Mars Astrobiology Research and Technology Experiment), uses samples taken from the area to find clues as to how life evolved and developed in other part of the universe, including Mars.