Mineral in crystal-clear form (4)

I believe the answer is:

talc

'mineral' is the definition.
(talc is a kind of mineral)

'in crystal-clear form' is the wordplay.
'in' indicates a hidden word.
'TALC' is hidden within 'crystal clear form'.

(Other definitions for talc that I've seen before include "soother" , "Scented powder used after bathing" , "Mica - scented body powder" , "Fine powder" , "Magnesium silicate powder" .)

I've seen this clue in The Globe and Mail and The Telegraph.

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