Its traces can be found from antiquity. It came back into fashion in the 12th century and then during the Renaissance.
White and translucent when pure, alabaster is often associated with various oxides, particularly iron, which gives it various colors (yellow, brown, red, orange, pink), often distributed in bands.
Mary, carries the child Jesus a cruciger orb symbol of the spiritual domination of Christ on the world and on the earth. We don't know who the third character is