a hard glossy mineral consisting of silicon dioxide in crystal form; present in most rocks (especially sandstone and granite); yellow sand is quartz with iron oxide impurities

a gemstone having the property of transmitting light without serious diffusion

an impure form of quartz consisting of banded chalcedony; used as a gemstone and for making mortars and pestles

green chalcedony with red spots that resemble blood

a translucent red or orange variety of chalcedony

a green variety of chalcedony valued as a gemstone

a chalcedony with alternating black and white bands; used in making cameos