The shafts were dug so that people could get at the flint lying at different depths. Flint veins were exploited by making numerous perforations of small diameter. This offered safety against possible cave-ins, and helped increase the amount of flint that could be obtained.
However, extraction work and digging became more difficult as the shafts became deeper. At greater depths visibility became poorer, the lack of space hindered digging, and it became ever harder to remove soil and stones to the surface.
The shafts at Casa Montero vary in depth from 0.63 - 9.26 m. The density of shafts is evidence of the use of the mine by several generations of Neolithic groups.
No shafts were found that crossed one another, indicating that the Neolithic miners who used the site knew the positions of earlier shafts. Rubble left at the surface probably identified those areas already mined.
Shafts from which flint was extracted were distinguishable from others that were not dug past the exploratory stage. The ‘exploratory’ shafts were no deeper than 1-2 m, stopping at clay levels where there was no opaline flint to extract. These exploratory shafts were always found at the edge of the site where the best flint runs out. The miners may have had very good geological knowledge of the area.
The ‘extraction’ shafts were very homogeneous in terms of their fillings and the material recovered from them, but variable in shape. Two types of extraction shaft were identified: ‘irregular’, with a sinuous profile and a maximum depth of about 2.5 m, and ‘chimney-like’ with regular, vertical walls and a depth of up to nearly 10 m.
The western limit of the site with a shaft exposing two veins of flint
Photo: The Casa Montero Team.
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