Ornamental stone, a variety of chalcedony (5)
I believe the answer is:
agate
I believe this is a double definition.
'ornamental stone' is the first definition.
(I've seen this before)
'a variety of chalcedony' is the second definition.
(I've seen this before)
(Other definitions for agate that I've seen before include "Stone with coloured bands" , "Variety of chalcedony" , "Impure form of quartz with banded chalcedony, used as a gemstone" , "rock with bands" , "Quartz variety" .)