Impure form of quartz used in making pestles and mortars (5)
I believe the answer is:
agate
(Other definitions for agate that I've seen before include "marble" , "Quartz gem" , "Type of quartz" , "Striped stone" , "Ornamental form of quartz" .)
I believe the answer is:
agate
(Other definitions for agate that I've seen before include "marble" , "Quartz gem" , "Type of quartz" , "Striped stone" , "Ornamental form of quartz" .)