Variety · Feldspar group
Moonstone
K(AlSi3O8) / Na(AlSi3O8) intergrowth
Moonstone is a gem variety of alkali feldspar (orthoclase or adularia intergrown with albite) showing a blue-white adularescence, from Sri Lanka, India, Myanmar and Switzerland's Alpine adularia. 'Rainbow moonstone' is actually labradorite. It is a lapidary and jewellery material rather than a crystal specimen.
| Formula | K(AlSi3O8) / Na(AlSi3O8) intergrowth |
|---|---|
| IMA status | variety |
| Crystal system | Monoclinic / triclinic |
| Mohs hardness | 6 |
| Group | Feldspar group |
| Type locality | None (variety) |
Fakes and treatments
Opalescent glass and synthetic spinel imitate moonstone; 'rainbow moonstone' is mislabelled labradorite.
Elsewhere
- Wikidata: Q430034
- Wikipedia: moonstone
- Mindat: Moonstone
Cite this article
Stratum Study. "Moonstone" (Mineral). Stratum Study pack 2026.09, as of 2026-09-19. https://stratum.black/study/minerals/moonstone. Accessed 2026-09-20.
@misc{stratum-moonstone,
title = {Moonstone},
author = {{Stratum Study}},
howpublished = {\url{https://stratum.black/study/minerals/moonstone}},
year = {2026},
note = {Mineral article, Stratum Study pack 2026.09, as of 2026-09-19; sources: stratum, wikidata, commons. 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.