The increased demand for zinc and lead during the 19th century attracted Spanish and foreign investors to Cantabria. The reports drafted by the mining engineer Pio Jusué y Barreda about the existence of calamines on the Cantabrian coast led to the commissioning of many studies about the seams in the region.
The work commenced by Grupo Minero La Florida in the Mountains of Arnero, where El Soplao Cave is located, is considered to be related to the constitution of the Compañía de Minas y Fundiciones de la Provincia de Santander (Compagnie des Mines et Fonderies de la Province de Santander) in Paris in 1855, for the purpose of exploiting, among others, the sites of Udías and Comillas.
On 11 November 1857 Queen Isabel II authorised the operation of the zinc mine "La Isidra". This is a particularly relevant document, since it makes the first reference to the mining site.
During the early stages, the activity was focused on the exploitation of calamines (a zinc carbonate mixture), and subsequently, lead sulphide (galena) and zinc (blende), obtained as the mines became deeper. Shortly afterwards, the seams were exploited using a combined system of tunnels and open-cast techniques.
Practically, all the mineral was shipped to ports in northern Europe based on the contract signed with the "Société des Mines et Fonderies de Zinc de la Vieille-Montagne" (Liège-Angleur, Belgium). At first, 90% to 95% of the mineral was shipped to Antwerp (Belgium). Later, it was also exported to Great Britain and France, with only 3% of the mineral remaining in Spain.
Between 1855 and 1860 a considerable development took place, and in 1859 there were 540 miners working in the mine, with jobs for another 60 people involved in transporting and loading the mineral.
In 1885, the "Compañía de Minas y Fundiciones de la Provincia de Santander" was absorbed by the "Real Compañía Asturiana de Minas" (R.C.A.M.) or Compagnie Royale Asturienne des Mines, with Belgian capital, following a period marked by many litigations regarding mining concessions and by the decline in legislation and exhaustion in some of the mines that were being operated. This led to a new period marked by industrialisation and a radical transformation of the operating methods, thanks to greater investments.
With the mine in the hands of the R.C.A.M, an initial division of work took place between the groups "Primera y Otras" and "Pablo y Otras", which continued until the activity was halted for an unspecified time. The commencement of this, which is equally difficult to determine, is thought to be in 1928 approximately. From the human standpoint, it was a time of social conflict. Several strikes were organised in the early 20th century, calling for better pay and the reduction of working hours.
This first closure led to serious difficulties for the inhabitants of the surrounding townships, who were unable to understand why the mine was closed since it was fully operational. The consequences were massive lay-offs and emigration.
The second phase of the activity, which started some time after the Spanish Civil War, gave rise to an important increase in production, associated with the growing degree of mechanisation and important changes in mining methods, with the creation of new interior slopes and tunnels for transportation and drainage. Examples of those mechanisation processes (even though we may find them elementary today) include the replacement of animals pulling the wagons with locomotives or the installation of electrical transformers for energy supply.
For 20 years before the closing of the mine, which took place in December 1978 (although it was officially closed at the start of 1979), those improvements made it possible to extract average annual amounts of about 75,000 tons, with average percentages of 4.5 and 0.6% for zinc and lead, respectively. This was the mine's most expansive period.
The mine was closed not because of the exhaustion of the seams, but because of financial difficulties. In 1981 the R.C.A.M. finally sold off all its rights to Asturiana de Zinc (AZSA). This again led to massive lay-offs and emigration and the end of the economic development of the valleys. Some fortunate miners were relocated in other facilities of the Real Compañía in the region, such as the molten blende mines of Áliva or the zinc mine of Reocín. Furthermore, many of the abandoned facilities suffered deterioration due to the passing of time and the harsh weather conditions.
All these processes modelled the landscape, leading it to change from traditional agrarian pastures to a different type of industrial landscape, which, today, contains a vast and insurpassable legacy of industrial mining archaeology for Cantabria, with special emphasis on the washing zones and calcining furnaces of Plaza del Monte, the derrick and pit of Lacuerre and the uninhabitated town of La Florida.
From the potholing perspective, the cave was explored in 1975 during the exploration and topographic works carried out by the Potholding Club of Cantabria (Speleo Club Cántabro or SCC. Some of the most unique elements of La Florida Mining Group are:
This is the oldest site and the one that gives the name to the mine. It was an open-cast mine and, today, the cavities and trenches created by the mining activity can still be seen. Next to it, there is a mining town (now uninhabited) which once had a chapel and school, a washing place, a powder house, stables, etc.
This is one of the oldest tunnels, opened between 1908 and 1910. It is now the access that leads to El Soplao Cave for the two types of tourist visits.
It has a depth of 167 m and was used as a mine until the opening of the general transport level of Cereceo, and from then on it was used exclusively by the workers. The transformer, the compressor building and the building that houses the pit elevator machinery still exist, as well as other auxiliary constructions, drainage ducts, a gravity tank, air chimneys and shafts.
This provisional mining tunnel ended up being used as an ore-dumping hole from ramp 4, allowing the ore to be brought out through the general transportation tunnel of Cereceo. The mechanical preparatory work was carried out in an area near the shaft. For the calamines, this was reduced to striating by hand, separating the sterile elements from the soil which was sent to the site for washing thick mineral for calcination. The blende was treated in a flotation workshop. The turret and head of the aerial cable are especially interesting as well as the washing sites and the calcining furnace. There are also other buildings in differing conditions of conservation. These include houses, the transformer, the compressor building, etc. La Plaza del Monte was the point of union with the rest of La Florida mine since it received most of the minerals that were obtained.
This is the most recent part of the mine. This 3,250 metre-long transportation tunnel was opened up for the purpose of connecting the Cereceo washing facilities with the mineralised areas of Cereceo, La Isidra and Lacuerre, thereby allowing the elimination of the old bucket line used for leading the ore and waste to the treatment facilities. The washing sites can still be seen, with their decanting ponds, the pit opening and the remains of an overhead cable. Other important buildings that once existed are the offices, hospital, houses, several tanks, coal bunkers, store, watch tower, powder house, laboratories, workshops, garages, etc.
Following the transfer of the Cereceo washing site to La Plaza de Monte, a new town was established, Caviña (also known as La Florida), which replaced the old settlement of La Florida. Both the living and administrative structures were reorganised in this area, with offices, a hospital, houses (including one for the manager), a store and a chapel, etc. At present it is inhabited and operative, but has no relationship with the intrinsic functions of the mining activity.
El Soplao Cave is closely linked to the work of La Florida Mining Group. As mentioned above, at first the mining activity was carried out in an open cast mine on the hill of La Florida. Between 1908 and 1910 work was started on the underground galleries through the construction of La Isidra tunnel. During this operation, the miners discovered a cave in the mountainside. This first contact with the cave was probably not welcomed by the company and managers, since the cavity obviously meant that there was no mineral.
However they quickly made use of these natural galleries excavated with great patience by the water for thousands of years, adapting them to connect different mining fronts throughout the mountain, in order to transport people and mineral or to provide oxygen for the mining tunnels.
Although some parts of this cave were adapted, the miners respected both the cave and the rock formations and merely created transportation spaces (for people and for the wagons laden with the orel) for the installation of machinery or building of structures linked to their activity, such as water harnessing devices, which can be seen scattered throughout the different parts of the cave.
In this way, the beauty of the geological heritage and the surprising industrial mining archaeology of our forefathers were naturally and subtly united.