The erosion caused by rain and wind creates canyons improperly called stone-pits.

These successive erosion gullies form focusing scree rocks at the bottom of the natural excavations.

To avoid unnecessary work we select certain pieces in site, based on specific criteria by clearing certain parts of their sandy gangues that are found at the gullies bottom, this first work is called graying!

Without modern means, extracting some blocks is painful and perilous; stone-hunters, with ropes and their oxen, back the stones of these lowlands.