Answer:

onyx

Answer	Crossword Clue
ONYX	Cameo stone
ONYX	Chalcedony
ONYX	Intaglio stone

ONYX	Cameo appearance?
ONYX	Stone meaning "fingernail" in Greek
ONYX	Agate variety
ONYX	Cameo gemstone
ONYX	Cameo mineral
ONYX	Black stone
ONYX	Jet black
ONYX	Stone used for cameos

ONYX	Quartz variety
ONYX	Banded chalcedony
ONYX	Jet-black
ONYX	Jet-black stone
ONYX	Jet-black gem
ONYX	Cameo material
ONYX	Stone seen in Mammoth Cave National Park
ONYX	Semiprecious stone

ONYX	Layered chalcedony
ONYX	Multicolored stone
ONYX	Ornamental chalcedony
ONYX	Type of quartz
ONYX	Black quartz
ONYX	Banded quartz
ONYX	Shade of black
ONYX	Ancient birthstone for July

ONYX	Black gemstone
ONYX	Banded gemstone
ONYX	Cameo gem
ONYX	Multicoloured agate
ONYX	Variety of agate
ONYX	Figurine mineral
ONYX	Multicolored agate
ONYX	Figurine agate

ONYX	Mineral that's often black
ONYX	Banded gem
ONYX	Banded quartz stone
ONYX	Banded cameo material
ONYX	Gem with colored bands