 In the early days of jade carving, quartz, a mineral with a high hardness level, was the object of choice.At the beginning of the Song dynasty, a time of prolific technology growth, "red sand", with a hardness level of 7.5 became the dominant tool of the industry.By 1939, and once more advanced carving tools had arisen, Peking jade carvers were already using six different types of abrasives