In geology, rock or stone is a naturally occurring solid aggregate of minerals and/or mineraloids.

The Earth's outer solid layer, the lithosphere, is made of rock. Three majors groups of rocks are defined: igneous, sedimentary, and metamorphic. The scientific study of rocks is called petrology, which is an essential component of geology.

Rocks are generally classified by mineral and chemical composition, by the texture of the constituent particles and by the processes that formed them. These indicators separate rocks into three types: igneous, sedimentary, and metamorphic. They are further classified according to particle size. The transformation of one rock type to another is described by the geological model called the rock cycle.

Igneous rocks are formed when molten magma cools and are divided into two main categories: plutonic rock and volcanic. Plutonic or intrusive rocks result when magma cools and crystallizes slowly within the Earth's crust (example granite), while volcanic or extrusive rocks result from magma reaching the surface either as lava or fragmental ejecta (examples pumice and basalt).

Gog and Magog (Hebrew: גּוֹג וּמָגוֹג‎‎ Gog u-Magog; Arabic: يَأْجُوج وَمَأْجُوج‎ Yaʾjūj wa-Maʾjūj) are names that appear primarily in various Jewish, Christian and Muslim scriptures, as well as numerous subsequent references in other works. Their context can be either genealogical (as Magog in Genesis 10:2) or eschatological and apocalyptic, as in Ezekiel and Revelation. They are sometimes individuals, sometimes peoples, and sometimes geographic regions. The passages from Ezekiel and Revelation in particular have attracted attention due to their prophetic descriptions of conflicts said to occur near the "End times".

The etymology of both the names Gog and Magog remains uncertain. The ma- at the beginning of Magog may indicate a land, or it may mean "from", so that Magog means "of the land of Gog" or "from Gog". Gog may originate as the Hebrew version of the name of Gyges of Lydia, who made his kingdom a great power in the early 7th century BC, but this explanation, although common, is not universally accepted. A different theory is that "Magog" might be a reference to Babylon, by turning BBL ("Babylon" in Hebrew script, which originally had no vowel-signs) into MGG (Magog), but this account, like the others, has problems.