Mineral

A mineral is a solid substance formed naturally, with a definite chemical composition and crystalline structure—meaning that its atoms are arranged in a repeating pattern. Minerals make up rocks, and earth science regards minerals as the fundamental building blocks of the planet's crust.

In Somali, the term 'macdan' is also used broadly for resources extracted from underground—such as gold, iron, petroleum, and gas. This commercial usage differs from the strict scientific definition, since petroleum and coal lack crystalline structure.

Properties for identification

Minerals are distinguished by measurable properties: color, the color of the powder left by scratching the surface (streak), shine on the surface (luster), hardness measured on the Mohs scale (ranging from talc to diamond), how they break (cleavage or fracture), and density. These properties arise from how atoms are bonded within the crystal.

Classification

Minerals are generally divided into chemical classes: silicates, oxides, sulfides, carbonates, sulfates, halides, phosphates, and native elements such as pure gold. Silicates are the most abundant mineral class in Earth's rocks, with feldspar and quartz among the most common minerals in the crust.

Formation

Minerals form from cooling magma, hot water moving through rock or cooling from it, pressure and heat that alter existing rock (metamorphism), and biological processes such as the accumulation of marine organisms that produce carbonate. Crystal size typically depends on cooling rate: slow cooling produces large crystals.

Economic value

Some minerals have industrial value and are called ore when they contain a useful element in sufficient concentration to be extracted profitably. For example, hematite and magnetite yield iron, bauxite yields aluminum, and chalcopyrite yields copper. Other minerals such as diamond, marble, and limestone are used directly.