The term "Serpentine" includes maybe 20 related minerals. These fall into two different groups - the antigorites and chrysotiles. Antigorites are solid and platy. They look much like jade and are used in gemstones and statues. The chrysotile group are fibrous and contain a type of asbestos. The above example is from the chrysotile group. Because the various serpentine minerals differ in composition, hardness levels in the group vary from 3 to 6. That makes it softer than granite but harder than most marble. It was used in architecture during the first half of the 1900's but fell out of use due to concerns about worker safety due to the asbestos content.