Blue-green gemstone (5)
This clue is a double definition.
'blue' is the first definition.
(thesaurus)
'green gemstone' is the second definition.
(I've seen this in another clue)
(Other definitions for beryl that I've seen before include "Girl's name - jewel" , "Gemstone of which emerald is a variety" , "Girl's name - precious stone" , "Green stone" , "Precious stone of which emerald is a variety" .)
(Other definitions for turquoise that I've seen before include "Greenish-blue gem" , "Bluey-green" , "Greenish-blue colour" , "Aquamarine colour" , "Birthstone for December" .)