Where it forms, where it's found
- Geological setting
products of the final stage of hydrothermal activity in association with greisenization.
- Type locality
- Vein No. 2
- Tsukubara mine
- Kiryu City
- Gunma Prefecture
- Japan
36.5114°, 139.4239°
1recorded occurrences
Physical
Optical
- UV response
- none
Crystallography
- Space group
- R-3m
- Cell parameters
- a = 6.9972(2) Å · c = 50.270(2) Å
- Z
- 3
- Type-locality form
occurs as the core in hexagonal tablet crystals, and gorceixite and goyazite like mineral with a zonal texture due to the Sr-Ba content are often present at the rim. The outermost rim in the yellow crystal consists of kintoreite or segnitite. The relationship between the core and rim is occasionally reversed, with gunmaite located at the rim. The diameter of the hexagonal crystals can be up to 500 μm, with a thickness of less than 100 μm in many cases. The gunmaite areas are euhedral to subhedral, and up to 200 micrometers in diameter.
- Comment
crystals contained stacking faults
Chemical composition
Synonyms
- Gunmaiet
- IMA2022-080
In other languages
- German
- Gunmait · IMA 2022-080
- Japanese
- 群馬石
Classification
Strunz
10th ed.8.BM
- 8Phosphates, Arsenates, VanadatesClass
- 8.BPhosphates, etc., with additional anions, without H2ODivision
- 8.BMWith medium-sized and large cations, (OH, etc.):RO4 = 4:1Group
- 8.BMGunmaiteSpecies
Literature, links & citation
Citations
- 2020mdcl.issp.u-tokyo.ac.jp (2020) https://mdcl.issp.u-tokyo.ac.jp/denken/?page_id=20#a26
- 2022Miyawaki, Ritsuro, Hatert, Frédéric, Pasero, Marco, Mills, Stuart J. (2022) IMA Commission on New Minerals, Nomenclature and Classification (CNMNC) – Newsletter 70. European Journal of Mineralogy, 34 (6) 591-601 doi:10.5194/ejm-34-591-2022 DOI: 10.5194/ejm-34-591-2022
- 2023Nishio-Hamane, Daisuke, Yajima, Takeshi, Ikari, Issei, Ohki, Yoshiya, Hori, Hirofumi, Ohara, Yoshihiro (2023) Kiryuite and gunmaite, two new minerals from Tsukubara, Kiryu City, Gunma Prefecture, Japan. Journal of Mineralogical and Petrological Sciences, 118 (1) 230605 doi:10.2465/jmps.230605 DOI: 10.2465/jmps.230605
Cite this entry
@misc{mineral2026,
author = {Mineral Index editorial board},
title = {Gunmaite — Mineral Index},
year = {2026},
url = {https://mineralindex.org/minerals/gunmaite-470430},
note = {Accessed 2026-05-11}
}