A translucent form of gypsum (9)

I believe the answer is:

alabaster

(Other definitions for alabaster that I've seen before include "White or translucent mineral" , "White gypsum used for carving" , "that's smooth and white" , "Altar base (anagr.)" , "Altar base (anag)" .)

I've seen this clue in the Sydney Morning Herald.

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