Where it forms, where it's found
- Geological setting
In an alluvial placer deposit, in fine-grained intergrowth with other chromium oxide-hydroxide minerals
- Type locality
- Merume River
- Rest of Region 8
- Potaro-Siparuni Region
- Guyana
5.2667°, -59.8333°
2recorded occurrences
Physical
Optical
- Optical type
- Biaxial
- UV response
- Not fluorescent in UV
- Notes
RI is not reported for this species as the refractive indices are probably very high, and more impostantly, the mineral is very dark, approaching opaque. No reflected light studies are known.
Crystallography
- Cell parameters
- a = 4.492 Å · b = 9.860 Å · c = 2.974 Å
- Ratio a:b:c
- 1 : 2.195 : 0.662
- Z
- 4
- Morphology
Very rarely as "minute deep red to black prismatic crystals [60-200 microns in size] of bracewellite line microscopic fissures and vugs in merumite". bracewellite is not present in all alluvial grains of merumite and, when present, has been found to constitute negligible amounts and in rare cases, up to a dominant part, of a merumite grain.
- Comment
Space Group originally given is Pbnm
Crystal structure
Chemical composition
Synonyms
- Bracewelliet
- IMA1967-035
In other languages
- German
- Bracewellit · IMA 1967-035
- Italian
- Bracewellite
- Chinese
- 羟铬矿
Classification
Strunz
10th ed.4.FD.10
- 4OxidesClass
- 4.FHydroxides (without V or U)Division
- 4.FDHydroxides with OH, without H2O; chains of edge-sharing octahedraGroup
- 4.FD.10BracewelliteSpecies
Dana
8th ed.06.01.01.05
- 06Hydroxides and Oxides Containing HydroxylClass
- 06.01XO(OH)Type
- 06.01.01Diaspore group (Orthorhombic, Pnma or Pnmd)Group
- 06.01.01.05BracewelliteSpecies
CIM
—7.14.2
- 7Oxides and HydroxidesClass
- 7.14Oxides of CrGroup
- 7.14.2BracewelliteSpecies
Group, growth & confusion
Literature, links & citation
Citations
- 1976Milton, C., Appleman, D. E., Appleman, M. H., Chao, E. C. T., Cuttitta, F., Dinnin, J. I., Dwornik, E. J., Ingram, B. L. and Rose, H. J., Jr. (1976) Merumite, a complex assemblage of chromium minerals from Guyana. U.S. Geological Survey Professional Paper 887: 1-29.
- 1977Fleischer, Michael, Cabri, Louis J., Nickel, Ernest H., Pabst, Adolf (1977) New Mineral Names. American Mineralogist, 62 (5-6) 593-600
- 1997Anthony, J.W., et al. (1997) Handbook of Mineralogy, Vol. 3: 75.
- 2005(2005) Bracewellite. Handbook of Mineralogy. Mineralogical Society of America
Cite this entry
@misc{mineral2026,
author = {Mineral Index editorial board},
title = {Bracewellite — Mineral Index},
year = {2026},
url = {https://mineralindex.org/minerals/bracewellite-748},
note = {Accessed 2026-05-11}
}