A very hard, granular, crystalline, igneous rock consisting mainly of quartz, mica, and feldspar and often used as a building stone.
A hard white or colorless mineral consisting of silicon dioxide, found widely in igneous, metamorphic, and sedimentary rocks. It is often colored by impurities (as in amethyst, citrine, and cairngorm).
A hard crystalline metamorphic form of limestone, typically white with mottlings or streaks of color, that is capable of taking a polish and is used in sculpture and architecture.
An extremely compact, hard, granular rock consisting essentially of quartz. It often occurs as silicified sandstone, as in sarsen stones.
A semiprecious variety of agate with different colors in layers.
White or light-colored calcareous rock deposited from mineral springs,