UM1990-24-O:Al
Valid as an unnamed mineral
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Formula:
\sigma-Al2O3
Polymorph of:
Co-described with UM1990-23-O:Al. Primarily though to be the δ phase. Probably not identical to deltalumite (most of the PXRD line positions differ).
Also associated with corundum.
The association is found as polycrystalline spherules, ca. 0.1 mm in diameter; they stand for 2-3% of a heavy fraction of minerals separated from loam and sandy loam (Upper Pleistocene to Holocene age) in different locations. of Yakutiya, USSR. The aluminous spherules are confined to layers, connected with formation of cryogenic soils. These metastable alumina polymorphs are though to be formed due to dehydration of colloidal aluminum hydroxides at subfreezing temperatures in the presence of saline pore solutions. They come from natural exposures within an uninhabitated area.
Also associated with corundum.
The association is found as polycrystalline spherules, ca. 0.1 mm in diameter; they stand for 2-3% of a heavy fraction of minerals separated from loam and sandy loam (Upper Pleistocene to Holocene age) in different locations. of Yakutiya, USSR. The aluminous spherules are confined to layers, connected with formation of cryogenic soils. These metastable alumina polymorphs are though to be formed due to dehydration of colloidal aluminum hydroxides at subfreezing temperatures in the presence of saline pore solutions. They come from natural exposures within an uninhabitated area.
Unique Identifiers
Mindat ID:
51812
Long-form identifier:
mindat:1:1:51812:5
GUID
(UUID V4):
(UUID V4):
84265903-7f27-425d-b6ad-1c17d5fc021e
Classification of UM1990-24-O:Al
IMA status notes:
Unnamed (probably valid)
Chemical Properties of UM1990-24-O:Al
Formula:
\sigma-Al2O3
Elements listed:
X-Ray Powder Diffraction
Powder Diffraction Data:
d-spacing | Intensity |
---|---|
2.76 Å | (20) |
2.59 Å | (10) |
2.43 Å | (30) |
2.30 Å | (20) |
2.11 Å | (10) |
2.01 Å | (30) |
1.96 Å | (20) |
1.52 Å | (10) |
1.39 Å | (100) |
Comments:
weak and diffuse lines; the most intense line coincides with the corresponding one of deltalumite's pattern
Other Information
Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.
Internet Links for UM1990-24-O:Al
mindat.org URL:
https://www.mindat.org/min-51812.html
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Please feel free to link to this page.
Mineral Dealers:
References for UM1990-24-O:Al
Reference List:
Localities for UM1990-24-O:Al
ⓘ - Click for references and further information on this occurrence.
? - Indicates mineral may be doubtful at this locality.
- Good crystals or important locality for species.
- World class for species or very significant.
(TL) - Type Locality for a valid mineral species.
(FRL) - First Recorded Locality for everything else (eg varieties).
Struck out - Mineral was erroneously reported from this locality.
Faded * - Never found at this locality but inferred to have existed at some point in the past (e.g. from pseudomorphs).
All localities listed without proper references should be considered as questionable.
All localities listed without proper references should be considered as questionable.
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