Mineral's in there, mixed with phosphorus (8)

I believe the answer is:

nephrite

'mineral's' is the definition.
(nephrite is a type of mineral)

'in there mixed with phosphorus' is the wordplay.
'mixed with' indicates an anagram.
'phosphorus' becomes 'P' (P is the chemical symbol for phosphorus).
'in'+'there'='inthere'
'inthere' anagrammed with 'p' makes 'NEPHRITE'.

I've seen this clue in The Guardian.

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