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The digging of a vault
The digging of
the lateral chimneys
Gradual progress
Gallery
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Map of mines layout in Gargas, courtesy of the Janselme family"
EXPLOITING THE OCHRE IN OPEN-AIR OR IN GALLERIES?
Depending on the quantity of earth and rock covering the ore, the ochre was exploited either in galleries or in open-air.
THE OPEN-AIR QUARRIES
In open-air, the layer of "sterile" is removed before reaching the exploitable area.
The cutting fronts can be as high as 20m and this way of extraction has left spectacular landscapes.
The ochre cliffs are the result of the combined efforts of man and nature.
THE UNDERGROUND GALERIES
If the sterile layer is too thick, it is more profitable to dig galleries into the rock.
The foreman determines where to start. The front miner digs into the wall either a diagonal ribbed vault or an arched vault.
Then two other miners, a left-handed one and a right-handed one, dig up a very narrow chimney on each side of that vault.
They will dig as deep as the combined length of their arm and of their pickaxe.
The central block thus isolated is destroyed with explosive. The work of progress goes on in the same way. The ore is
carried out to the outside in wagons pulled by mules.
From 1885 on, the galleries are straight. They can be as high as 10m to 15 m by 3 m wide.
There has never been a need to shore up the galleries, by the compactness of the ore and the fact that the tunnels are
separated by pillars of 6m by 6m.
In some quarries the two ways of extraction are used simultaneously, offering cutting fronts with holes in it. Nowadays,
the exploitation of ochre is only permitted in open-air quarries.
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