They are often larger, rounded stones that have been smoothed by both glacial and fluvial actions over time and deposited in the region by the Rhône.[2][3]
Galets roulés (means rolled pebbles) are predominantly quartzite and are thought to be integral to the growth of vines and more importantly, the ripening of the fruit[4] by absorbing the heat from the daytime sunshine and then releasing that heat slowly overnight due to their natural capacity for heat retention and transmission.[5] This is well suited to the Grenache variety that is widely grown and is the base of much of the red wines produced in the region. Galets roulés also serve to protect the vine and minimize soil erosion during the periods of strong winds that are known in the area as mistral.
