How geology created and technology dismantled the Roman “Gypsum Empire”
Natural resources do more than supply materials. Occasionally, they reorganize entire economies. In central Spain, near Segóbriga, an unusual mineral lapis specularis, a transparent gypsum became the Roman world’s substitute for window glass and powered a regional mining boom.
Our recent research synthesizes archaeological, geological and historical evidence showing that this was not a small quarrying activity but a large, organized extractive district with kilometres of underground galleries, engineered drainage, and state-regulated production. The scale rivals other major Roman mining regions.
Read the full study here:
https://doi.org/10.1007/s12371-026-01268-9
What makes the case remarkable is not only its size but its logic.
The mineral behaved like a technology. It enabled light, insulated interiors and architectural comfort centuries before flat glass became common. Demand from baths, villas and public buildings turned Segóbriga into a prosperous mining municipium connected to Mediterranean trade routes.
But the same factors that created the boom also made it fragile.
The deposits were irregular paleokarst pockets rather than continuous beds. Extraction was labor-intensive, deep and costly. When flat glass manufacturing improved, glass offered a cheaper, scalable substitute. The market shifted rapidly.
The mines did not run out.
They became economically obsolete.
This transition illustrates a pattern familiar today: technological substitution can erase entire resource systems, no matter how sophisticated. Lapis specularis played the role that whale oil, natural ice or photographic film would later play in other eras.
Segóbriga therefore represents more than Roman mining heritage. It preserves a complete socio-technical landscape where geology, engineering, labor organization and innovation intersect. Few places show so clearly how natural resources can shape and abruptly unshape societies.
Related work by the authors on mineral resources and their broader societal implications:
https://link.springer.com/search?query=Antonio%20Alonso-Jim%C3%A9nez%20mineral%20resources