geology Geology () is a branch of natural science concerned with Earth and other Astronomical object, astronomical objects, the features or rock (geology), rocks of which it is composed, and the processes by which they change over time. Modern geology ...

and mineralogy, a mineral variety is a subset of a mineral species or

mineraloid A mineraloid is a naturally occurring mineral-like substance that does not demonstrate crystallinity. Mineraloids possess chemical compositions that vary beyond the generally accepted ranges for specific minerals. For example, obsidian is an a ...

with some special characteristic, such as specific impurities or structural defects.A. S.Povarennykh (1972): "The Mineral Species as a Basic Concept of Mineralogy", pages 79-80. In: ''Crystal Chemical Classification of Minerals'', Springer For example,

amethyst Amethyst is a violet variety of quartz. The name comes from the Koine Greek αμέθυστος ''amethystos'' from α- ''a-'', "not" and μεθύσκω (Ancient Greek) / μεθώ (Modern Greek), "intoxicate", a reference to the belief that ...

is a variety of

quartz Quartz is a hard, crystalline mineral composed of silica ( silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical f ...

with a purple tinge due in part to

iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in ...

impurities. Mineral varieties can be further subdivided into sub-varieties. Unlike mineral species, mineral varieties are not defined or named by the International Mineralogical Association (IMA).

References

Mineralogy {{mineral-stub

See also

References