What is the definition of a rock?

Question

What is the definition of a rock?

Answer 1

Short and sweet: A rock is an aggregate of minerals

Mineral: A distinct chemical formula

First things I learned in geology

Answer 2

Rocks are classified as igneous, sedimentary and metamorphic.  Mineral rocks contain minerals in them such as iron, nickel, cobalt, gold, silver, etc.

You'll never look at a rock the same way again after you pick up a book on mineral rocks.  The photos illustrate the beauty of the mineral world vividly.  On earth, most of the rocks combined with oxygen to form oxides.  On the moon, there are mostly silicates.  Extracting a metal from rocks is the science of metallurgy.

Many planets and moons are rocks with iron and nickel cores which hold the potential for becoming dynamos.  A dynamo is the magnetic field which protects us from cosmic rays, while an atmosphere protects us from uv, gamma and x-rays.  Mars had a geologically active dynamo billions of years ago, but it cooled and is now defunct.  It may be possible to re-activate it someday by inserting a Superconducting Ring made of Iron doped with Arsenic.

Answer 3

In geology, rock is a naturally occurring aggregate of minerals and/or mineraloids. The Earth's lithosphere is made of rock. In general rocks are of three types, namely, igneous, sedimentary, and metamorphic. Petrology is the scientific study of rocks.

Rocks are 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 igneous, sedimentary and metamorphic. They may also be classified according to particle size, in the case of conglomerates and breccias or in the case of individual stones. 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 (eg. granite), while volcanic or extrusive rocks result from magma reaching the surface either as lava or fragmental ejecta (eg. pumice and basalt) .

Sedimentary rocks are formed by deposition of either clastic sediments, organic matter, or chemical precipitates (evaporites), followed by compaction of the particulate matter and cementation during diagenesis. Sedimentary rocks form at or near the Earth's surface.

Metamorphic rocks are formed by subjecting any rock type (including previously-formed metamorphic rock) to different temperature and pressure conditions than those in which the original rock was formed. These temperatures and pressures are always higher than those at the Earth's surface and must be sufficiently high so as to change the original minerals into other mineral types or else into other forms of the same minerals (e.g. by recrystallisation).

For example: Marble is formed when limestone gets metamorphosed.