natural glass - magma of any composition that cooled very rapidly

quartz crystal - a thin plate or small rod of quartz cut along certain lines and ground so that it can produce an electric signal at a constant frequency; used in crystal oscillators

atomic number 14, silicon, Si - a tetravalent nonmetallic element; next to oxygen it is the most abundant element in the earth's crust; occurs in clay and feldspar and granite and quartz and sand; used as a semiconductor in transistors

mineral - solid homogeneous inorganic substances occurring in nature having a definite chemical composition

rock crystal, transparent quartz - a clear quartz used in making electronic and optical equipment

cairngorm, smoky quartz - a smoky yellow or brown quartz

amethyst - a transparent purple variety of quartz; used as a gemstone

calcedony, chalcedony - a milky or grayish translucent to transparent quartz

citrine - semiprecious yellow quartz resembling topaz

rose quartz - a translucent rose-red variety of quartz used for ornaments

silica, silicon dioxide, silicon oxide - a white or colorless vitreous insoluble solid (SiO2); various forms occur widely in the earth's crust as quartz or cristobalite or tridymite or lechartelierite

aventurine, sunstone - a translucent quartz spangled with bits of mica or other minerals

common topaz, false topaz, topaz - a yellow quartz