Twinning

Intergrowth of two or more crystals of the same mineral in a symmetrical relationship: contact twins (spinel, gypsum swallowtail), penetration twins (staurolite crosses, fluorite cubes), repeated twins (plagioclase striations).

Sources

Earle, S. (2019). Physical Geology, 2nd ed., Chapter 2: Minerals (CC BY 4.0)
Mindat — Mineralogical glossary (link only)

Cite this article

Stratum Study. "Twinning" (Glossary). Stratum Study pack 2026.09, as of 2026-09-16. https://stratum.black/study/glossary/twinning. Accessed 2026-09-20.

BibTeX · CSL-JSON

@misc{stratum-twinning,
  title        = {Twinning},
  author       = {{Stratum Study}},
  howpublished = {\url{https://stratum.black/study/glossary/twinning}},
  year         = {2026},
  note         = {Glossary article, Stratum Study pack 2026.09, as of 2026-09-16; sources: stratum. Accessed 2026-09-20.}
}

Citations carry the pack version and the article's as-of date so they resolve to the same text later. The facts themselves belong to the sources listed below; cite those for the science.