Little school of mineralogy
What is a mineral?
A mineral is a natural formation, created as a result of natural physical and chemical processes, with a specific chemical composition and crystal structure, stable under certain conditions of temperature and pressure.
What is the origin of the term mineral?
The term mineral is derived from the Latin word mineralis, meaning ore-related, i.e. originating from a mine, and dates back to the earliest period in which people used numerous minerals to obtain various metals.
Are the terms mineral and crystal synonymous?
No. In nature, a mineral can appear in the form of a crystal – a regular geometric body with a certain degree of symmetry, but it can also appear in the form of various irregular accumulations called aggregates.
Therefore, not every mineral is necessarily a crystal, but every crystal is a mineral.
What are minerals made of?
Minerals are composed of atoms or ions connected by different types of chemical bonds, covalent, ionic, metallic, Van der Waals forces or hydrogen bonds, which repeat regularly in space.
The regular spatial arrangement of atoms or ions within a mineral is called the mineral structure.
How and why do minerals differ from one another?
Due to their different chemical composition and structure, minerals differ from one another in a whole range of physical properties such as external form, i.e. morphology, optical properties, whether macroscopic, colour and streak, lustre, or microscopic, cleavage, fracture, hardness and density.
A smaller number of minerals are also characterised by specific magnetic and electrical properties, as well as fluorescence, phosphorescence or radioactivity.
What determines the external appearance of a mineral?
The external appearance of a mineral, its habit, is determined by its structure, i.e. its regular internal arrangement, but also depends on the conditions of crystallisation and crystal growth.
The habit of a mineral may be spherical, granular, columnar, barrel-shaped, needle-like, fibrous, platy, leafy, flaky, etc.
The external form of a crystal indicates the crystal system, cubic, tetragonal, hexagonal, orthorhombic, monoclinic or triclinic, in which the mineral crystallises.