Celestite (SrSO4) is a mineral consisting of strontium sulfate. It is named for its occasional delicate blue color.
It occurs crystallized, also in compact massive and fibrous forms.
... D'Orsay, actress (+ 1983)
April 22 - Robert Oppenheimer, physicist (+ 1967)
May 6 - Harry Martinson, swedish author, winner of the Nobel Prize in literature
May 11 ...