Stated amounts of liquid that can be found in minerals (6)
I believe the answer is:
quartz
'can be found in minerals' is the definition.
'stated amounts of liquid' is the wordplay.
'stated' indicates a 'sounds like' (homophone) clue.
'amounts of liquid' becomes 'quarts'.
'quarts' is a homophone of 'QUARTZ'.
'that' is the link.
(Other definitions for quartz that I've seen before include "Silicon dioxide mineral" , "Type of watch and crystal" , "Crystalline mineral" , "Hard silica mineral" , "Stone such as amethyst or cairngorm" .)