Occasionally have tea black, or a mineral? (4)

I believe the answer is:

talc

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

I don't understand how the remainder of the clue works.

(Other definitions for talc that I've seen before include "White powder for the bathroom" , "Drier" , "Soft mineral; powder" , "soother" , "Powdered mineral" .)

I've seen this clue in The Irish Times.

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