Serpentine is called Xiuyan jade, or Xiuyu jade, or new jade in China, and is often used as nephrite replacement. Is serpentine (or Xiuyan jade or Xiuyu jade, or new jade) a true jade?
The answer is NO.
There are only 2 TRUE jades: nephrite and jadeite.
Serpentine is a group of related minerals including antigorite and chrysotile. Serpentine is often translucent, has various colors including: white, yellow, green, gray, brown, etc. Serpentine has greasy, waxy, or silky look. Mohs hardness of serpentine is 2 - 5, a very soft stone. The two most common members of the serpentine group are:
Antigorite - (Mg,Fe)3Si2O5(OH)4
Chrysotile - Mg3Si2O5(OH)4
Serpentine is very soft. You can easily scratch the surface of serpentine with a metal nail. Serpentine changes color over time which is called "zuoshui" in China, indicating the change of mineral composition over time.
Nephrite jade consists of calcium- and magnesium-rich amphibole mineral actinolite with mineral formula of : Ca2(FeMg)5(OH)2(Si4O11)2.
Nephrite jade is a very hard and very strong stone, with Mohs hardness of 6.0 - 7.0. Nephrite jade is harder than steel. You CANNOT scratch the surface of nephrite with a metal nail.
Color of nephrite jade can be white, green, gray, brown, yellow, black etc.
Because of the color similarity, serpentine is often used in China to make fake nephrite jade products.
Some fake nephrite jade egg examples made from serpentine (xiuyan or xiuyu jade):
Don't buy fake jade eggs made of marble stones, buy real jade eggs made of genuine nephrite jade.