Naturally pink common opal from Peru. Most people think of flashy precious opal from Australia, but opal actually occurs in various colours and around the world. The non-flashy type is often referred to as common opal. This specimen is discreetly glued to a square black plastic base.
The final photo shows examples of all the different colours and forms of opal that I have on my web site (at least until some sell). Just put "opal" into the search box to see them all.
5/8 inch (1.6 cm) wide, 7/16 inch (1.1 cm) deep and 1/2 inch (1.3 cm) tall.