Answer: tourmaline

AnswerCrossword Clue
TOURMALINESri Lanka export
TOURMALINEOne of October's birthstones
TOURMALINEStone obtained from granite
TOURMALINEAn October birthstone
tourmaline(French) a brittle boron aluminosilicate mineral with a glassy lustre, occurring as prismatic crystals of the trigonal system
tourmalineA brittle gray or black mineral that occurs as prismatic crystals in granitic and other rocks. It consists of a boron aluminosilicate and has pyroelectric and polarizing properties, and is used in electrical and optical instruments and as a gemstone