This instance is from Wikipedia and may be reused less than a CC BY-SA license. They can be sculpted into a variety of styles throughout this process, from time to time causing deep thumb-print like indentations on their own surfaces known as regmaglypts. From Wikipedia This example is from Wikipedia https://sculptedmdlakewood84219.madmouseblog.com/16962886/little-known-facts-about-sculpted-md-lakewood