Fuyuanite

Mg7Nb6O18(OH)8
IMA status
  • Approved
IMA symbol
Fuy
Also known as
  • Fuyuaniet
  • IMA2024-059

Where it forms, where it's found

Geological setting

More than 100 carbonatite dikes (1∼2 m wide, NNE to NNW orientation) coeval with the ore-hosting carbonatite pluton, intruded into the Archean-Mesoproterozoic basement complex and Mesoproterozoic sedimentary formation around the three open pits in Bayan Obo. These dikes can be categorized into three types based on their main mineral composition and sequence: the dolomite type, the dolomite-calcite type, and the calcite type, with progressively increasing REE content from early to late stages. The new mineral fuyuanite was found in a dolomite-calcite carbonatite dike.

Type locality
Bayan Obo deposit
  1. Bayan Obo mining district
  2. Baotou City
  3. Inner Mongolia
  4. China

41.7958°, 109.9694°

1recorded occurrences
Source · OpenStreetMap

Physical

Hardness
123456789104 – 5/ 10 MOHS
  1. 1Talc
  2. 2Gypsum
  3. 3Calcite
  4. 4Fluorite
  5. 5Apatite
  6. 6Orthoclase
  7. 7Quartz
  8. 8Topaz
  9. 9Corundum
  10. 10Diamond
Transparency
Translucent
Colour
reddish-brown to brown
Streak
reddish-brown
Cleavage
Distinct/Good

good to fair cleavage along the (001) plane

Density
4.156 g/cm³

Optical

Pleochroism
Visible

from orange-red to pale yellow under cross-polarized light.

Reflectance R%
(11.0,10.3) 470, (10.7,10.1) 546, (10.6,10.1) 589, (10.6,10.2) 650
Notes

The refractive indices of fuyuanite are too high to be measured using the available index liquids.

Reflected-light panel
10.7 %anisotropic · dual curve
Specimen sRGB 123, 85, 45
White reference100 % reflector under same lamp
R₁ R₂
Mode

Crystallography

Crystal system
Trigonal
Space group
#79
Cell parameters
a = 10.7174(5) Å · c = 4.7110(2) Å
Z
1
Type-locality form

platy, euhedral to subhedral crystals ranging from 40μm to 60μm in size. Commonly occurs in the edges of oboniobite aggregates.

Comment

single-crystal

Chemical composition

Constituent elements
Mass composition breakdown
ElementAtoms At. mass g/mol Mass g/molMass share
41NbNiobiumNiobium692.906557.436
48.41%
8OOxygenOxygen2615.999415.974
36.12%
12MgMagnesiumMagnesium724.305170.135
14.77%
1HHydrogenHydrogen81.0088.064
0.70%
Total1151.609100.00%

Mass share = atoms × atomic mass ÷ molar mass × 100

From Mindat formula

Synonyms

  • Fuyuaniet
  • IMA2024-059

In other languages

German
Fuyuanit · IMA 2024-059

Classification

Strunz
10th ed.

4.CB

  • 4OxidesClass
  • 4.CMetal: Oxygen = 2: 3,3: 5, and similarDivision
  • 4.CBWith medium-sized cationsGroup
  • 4.CBFuyuaniteSpecies

Literature, links & citation

Citations
  1. 2025SHE, HaiDong; FAN, HongRui; ZHAN, YunXiang; GU, XiangPing; LI, XiaoChun; YANG, KuiFeng; WANG, QiWei (2025) A new hydroxyl niobic-magnesic oxide mineral in the Banyan Obo polymetallic deposit: Fuyuanite. Acta Petrologica Sinica, 41 (1). 1-3 doi:10.18654/1000-0569/2025.01.01DOI: 10.18654/1000-0569/2025.01.01
  2. 2025She, Hai-Dong; Fan, Hong-Rui; Zhan, Yun-Xiang; Gu, Xiang-Ping; Li, Xiao-Chun; Yang, Kui-Feng; Wang, Qi-Wei (2025) Fuyuanite [Mg7Nb6O18(OH)8], a new hydrous magnesic-niobic oxide mineral from the Bayan Obo deposit, China. American Mineralogist, 110 (10). 1649-1657 doi:10.2138/am-2024-9676DOI: 10.2138/am-2024-9676
Cite this entry
@misc{mineral2026,
  author    = {Mineral Index editorial board},
  title     = {Fuyuanite — Mineral Index},
  year      = {2026},
  url       = {https://mineralindex.org/minerals/fuyuanite-471493},
  note      = {Accessed 2026-05-11}
}