The Iberian Peninsula was rich in minerals in Antiquity. Since ancient times minerals were prospected, found and exploited by Phoenicians, Greeks, Carthaginians and Romans.
The fame of Hispania about this is summarized in the famous quote by Strabo referring to Turdetania (the south of the Peninsula, essentially present-day Andalusia) in Book III of his Geography, 2.8:
To the great wealth of this region adds mineral abundance. This is cause for admiration; because, although the whole land of the Iberians is full of them, not all regions are so fertile and so rich at the time, and especially those regions that are abundant in minerals, because they rarely happen both at the time, and it is also rare to be able to find all kinds of metals in a small region. But Turdetania and neighboring regions abound in both things, and there aren´t enough suitable words to evaluate precisely this wealth. So far, neither native gold, nor silver, nor copper, nor iron has been found anywhere else on earth so abundant and of such a high quality.
Not only the shiny silver from Cartagena or the shiny gold from the Northwest were sought. There is a nonmetallic mineral seemingly less noble but very important that the Romans exploited with relish, the selenite, a transparent plaster they called "lapis sepecularis" (speculate stone), eyeglass, similar to a mirror.
Its laminar configuration allowed its exfoliation in sheets of various thicknesses, cut to size, which served to cover windows or openings in the walls allowing the light to pass through them and protecting from the inclement weather. That is, the lapis specularis (speculate stone) served as crystal or glass, whose use would gradually catch on in the buildings.
The Latin author who gives more references about this is the naturalist and scientist Pliny the Elder, author of a kind of encyclopedia of Nature then called “Naturalis Historia” (Natural History). This Pliny is a science martyr because, during the eruption of Vesuvius that destroyed Pompeii, Herculaneum and other nearby points in the year 79 AD, in his effort to better understand the phenomenon, he not only didn´t run away in the fleet he precisely ruled, but approached the coast, where he was found dead the next morning suffocated by the lethal gases the volcano emanated.
With regard to this, Pliny says: III, 30:
"Almost the whole Hispania is abundant in lead, iron, copper, silver and gold metals; the Citerior is rich in selenite (lapis specularis), the Baetica is abundant in cinnabar. There are also quarries of marble"(Pliny the Elder: Naturalis Historia, Book III, 30).
metallis plumbi, ferri, aeris, argenti, auri tota ferme Hispania scatet, citerior et specularis lapidis, Baetica et minio. sunt et marmorum lapidicinae
And referring to lapis specularis in XXXVI, 162, he says:
Black stone is sometimes also found, but the wonderful feature of the white stone, despite its well-known softness, is that it resists the sun and cold.
invenitur et niger aliquando, sed candido natura mira, cum sit mollitia nota, perpetiendi soles rigoresque,
To measure the importance of this material that allows the light to pass through it, let´s think of the construction and urban zeal that characterizes the Roman culture and that was imposed wherever the Roman legions reached to dominate.
Well, the most important mines or quarries of this plaster in the Roman Empire, both in quantity and quality, were in Citerior Hispania, in a circle of a hundred thousand steps around the city of Segóbriga, as Pliny the Elder explicitly tells us in his famous work, Naturalis Historia , XXXVI, 160:
"These (the stones he speaks about) can be cut; but the “speculate stone”, because this one is also called stone, is separated into as thin as desired sheets by its own nature, much more manageable. A long time ago, only Citerior Hispania provided it, and not in the whole province, but in a space of a hundred thousand steps around Segóbriga city. Nowadays Cyprus, Cappadocia and Sicily also provide it and it has recently been found in Africa too, but all of them have to be postponed to that of Spain; in Cappadocia they are produced very large, but they are dark."
Et hi quidem sectiles sunt, specularis vero, quoniam et hic lapidis nomen optinet, faciliore multo natura finditur in quamlibeat tenues crustas. Hispania hunc tantum citerior olim dabat, nec tota, sed intra centum millia passuum circa Segobrigam urbem, iam et Cypros et Capadocia et Sicilia et nuper inventum Africa, postferendos tamen omnes Hispaniae, Cappadocia amplissimos magnitudine, sed obscuros."
Segóbriga is next to the current Saelices, in the province of Cuenca (Spain). By the way, the name of this city (Segóbriga) is a Celtic term which comes to mean "city" (briga; related to burg, element which forms the name of hundreds of cities and towns in Europe) and “victory” (Sieg, Seg; related to the current German substantive Der Sieg = victory).
The 100,000 steps Pliny determines are the equivalent of about 150 kilometers and certainly in that radius they are numerous the places which were rich in lapis specularis in the province of Cuenca, such as Osa de la Vega, Torrejoncillo del Rey, Torralba, Huete, … as it is confirmed by the archeology, which locates in the area 25 deposits in 15 municipalities, although this magnitude or number is not closed.
They began to be used like glass in the first century AD, at the end of the Republic, and especially systematically in the Empire, from Augustus.
It was extracted from deep wells up to 30 meters and galleries, because it is underground. Pliny the Elder tells us in Book XXXVI of his Natural History, 161:
In Hispania it is extracted from very deep wells, and it is often located underground embedded in the rock and it has to be extracted or cut, but the greatest part of it, due to its fossil nature, is found loose or released itself as a fragment, but the “speculate stones” are never greater in length than five feet. puteis in Hispania effoditur e profunda altitudine, nec non et saxo inclusus sub terra invenitur extrahiturque aut exciditur, sed maiore ex parte fossili natura, absolutus in se caementi modo, numquam adhuc quinque pedum longitudine amplior
Thus this material was extracted from the mine, in blocks of up to 1.5 meters of thickness, then it was outlined and cut in standardized pieces and at last it was finished or finally prepared in several sheets adapted to the window or opening in the placement site. The slides were encrusted or inlaid into a wood or metal frame as we do now with our current windows.
There were other stones with some similar feature, such as the one they called “lapis penghites”, marbled or mottled harder material produced in Cappadocia, but far from the qualities of transparency of the speculate stone= lapis specularis (Pliny, Nat. Hist. XXXVI, 163). Perhaps with that name they are referring to some sort of onyx or alabaster, translucent but not transparent.
The stone itself and its waste or remains had also other uses, as an ornamental and decorative stone to cover walls and floors because of the reflection it produced; as Pliny the Elder for example tells us again: Nat. Hist. 36, 162:
A different use was also found for it such as shavings and flakes to adorn the Circus Maximus in the Circus Games to make it a pleasant whiteness.
invenere et alium usum in ramentis squamaque, Circum maximum ludis Circensibus sternendi ut sit in commendatione candor.
Known is the passion of the Roman people for the horse and chariot races that were held at the circus, where teams competed identified by the color of their uniform and badge. The passions that these races originated are comparable only with the ones modern soccer or football raises, sport or show that it has many similarities sociologically with, which I will discuss at another time.
As Pliny tells us himself, the best plaster is the one coming from the lapis specularis, so its disposal, waste or remains served as forging plaster to manufacture stucco, moldings, castings, plastered walls, floors, domes, ceilings, etc. Nat. Hist. Book XXXVI, 182:
However, the best of all though is done of speculate stone and of that having such flakes.
omnium autem optimum fieri compertum est e lapide speculari squamamve talem habente.
Without further detail we can think about and reflect on the complexity of any mining or mineral exploitation of these dimensions in the ancient world: land survey, sample or tasting realization, determination of the mine which happens to be "ager publicus" or state land; operating and exploitation system, usually through a concession or lease upon payment of an amount, realization of technical works to open wells generally square of 2 x 2 meters and up to 30 meters deep, and horizontal galleries or with ramps, extraction of the material with the appropriate tools (picks, hammers, pointers, pliers, chisels, saws, etc.), aeration and ventilation, use of ropes, baskets and panniers of esparto, waterproofed baskets for water extraction, lamps and chandeliers usually of oil (fuel lasted about five hours), the transfer of the mineral to the surface, the preparation in the entrance or mouth of the mine.
Once the material was prepared, it was transported with carts, pulled by oxen rather than horses, to Carthago Nova, the largest and most important port in the Levant, by the main road which was precisely called "via spartaria" (esparto path or road) from Ercavica (near modern Cañaveruelas, close to Opta, the current Huete) to Segóbriga and Cartagena through Cuenca, Albacete and Murcia. Naturally, the important Roman road network is the infrastructure that partly explains and simultaneously is the effect of the efficient extraction of the Romans. Numerous milestones, milliarium, (similar to our current kilometer signals) that have appeared on the road and are commemorative of the High Empire period (first part of the Empire) give us an idea of its importance.
From Carthago Nova it is exported to other parts of the Empire, especially to Rome, Massalia (Marseille), Piraeus (Athens), Antioch, Leptis Magna and Karthago (in Tunisia), Alexandria…
It is likely that, as the mines were affected to the “fiscus” or imperial treasury or finances, the army itself collaborated on technical and organizational issues, as it also happened in the peninsular Northwest gold mines.
Although mines of Segóbriga are the most important ones, others were also exploited in Almería, area otherwise rich or abundant in other minerals and metals such as copper, silver, lead or marbles that were exploited since the second century BC.
The evolution in the manufacture or factoring of glass and its increasing or growing application ended with this “lapis specularis” (speculate stone) mining.