Birthstones for some Scorpios (5)
I believe the answer is:
opals
'birthstones for some scorpios' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for opals that I've seen before include "Milky-white stones" , "Milky gemstones with delicate colours" , "Precious stones" , "Semi-precious stones of milky or bluish colour" , "Iridescent gems" .)