In geology, a vein is a distinct sheetlike body of crystallized minerals within a rock. Veins form when mineral constituents carried by an aqueous solution within the rock mass are deposited through precipitation. The hydraulic flow involved is usually due to hydrothermal circulation.
White veins in dark rock at Imperia, Italy
A quartz vein, prominent from the surrounding weathered rock at Cape Jervis, South Australia
Boudinaged quartz vein (with strain fringe) showing sinistral shear sense. Starlight Pit, Fortnum Gold Mine, Western Australia.
In situ gold-bearing vein (in brown) at the Toi gold mine, Japan.
In geology, rock is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the minerals included, its chemical composition, and the way in which it is formed. Rocks form the Earth's outer solid layer, the crust, and most of its interior, except for the liquid outer core and pockets of magma in the asthenosphere. The study of rocks involves multiple subdisciplines of geology, including petrology and mineralogy. It may be limited to rocks found on Earth, or it may include planetary geology that studies the rocks of other celestial objects.
The Grand Canyon, an incision through layers of sedimentary rocks.
A balancing rock called Kummakivi (literally "strange stone")
Rock outcrop along a mountain creek near OrosÃ, Costa Rica.
Sample of igneous gabbro