These are centuries-old terracotta tiles that were used in the south of France as an underlayment for clay roof tiles. As the old roofs have been restored, some insightful French people have salvaged these unique tiles to set them on floors.
The average size is approximately 9" x 14", but may vary by as much as an inch. They are about 1" thick.
The coloration also varies from lot to lot. Some are quite red in complexion, while others are more ochre or brown. This board shows the tiles set in a "windmill" pattern with a dot made of "Devalliere Chateau" limestone (see "new/limestone") cut to fit. It is sealed with wax