quartz 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
transparent gem a gemstone having the property of transmitting light without serious diffusion
agate an impure form of quartz consisting of banded chalcedony; used as a gemstone and for making mortars and pestles
chrysoprase a green variety of chalcedony valued as a gemstone
onyx a chalcedony with alternating black and white bands; used in making cameos
plasma the colorless watery fluid of the blood and lymph that contains no cells, but in which the blood cells (erythrocytes, leukocytes, and thrombocytes) are suspended
Chalcedony is a cryptocrystalline form of silica, composed of very fine intergrowths of the minerals quartz and moganite. These are both silica minerals, but they differ in that quartz has a trigonal crystal structure, whilst moganite is monoclinic. Chalcedony's standard Chemical structure (Based on the chemical structure of quartz) is SiO2 (Silicon Dioxide).
