| Shigaite | |
|---|---|
 Reddish-brown shigaite crystal (2 cm across) with pink
rhodochrosite from South Africa | |
| General | |
| Category | Sulfate mineral |
|
Formula (repeating unit) | NaAl3(Mn2+)6(SO4)2(OH)18·12H2O [1] |
| IMA symbol | Sga [2] |
| Strunz classification | 7.DD.35 [3] |
| Dana classification | 31.1.2.1 [3] |
| Crystal system | Trigonal |
| Crystal class | Rhombohedral (3) H-M symbol: (3) [3] |
| Space group | R3 [4] |
| Unit cell | a = 9.51 Å, c = 32.83 Å, [3] Z = 3 [5] |
| Identification | |
| Color | Yellow, burnt orange, brown, black [5] |
| Twinning | On {0001} [5] |
| Cleavage | Perfect on {0001} [5] |
| Tenacity | Moderately flexible [5] |
| Mohs scale hardness | 2 [5] |
| Luster | Vitreous to dull [3] |
| Streak | Very pale yellow to white [5] |
| Diaphaneity | Transparent [3] |
| Specific gravity | 2.32 [4] |
| Optical properties | Uniaxial (−) [3] |
| Refractive index | n = 1.546 [4] |
| Pleochroism | Distinct; O = yellow; E = very pale yellow [5] |
| Ultraviolet fluorescence | Non-fluorescent [4] |
Shigaite is a mineral with formula NaAl3(Mn2+)6(SO4)2(OH)18·12H2O that typically occurs as small, hexagonal crystals or thin coatings. It is named for Shiga Prefecture, Japan, where it was discovered in 1985. [3] The formula was significantly revised in 1996, identifying sodium as a previously unknown constituent.
Shigaite occurs as hexagonal tabular crystals up to 2 cm (0.79 in) in size or as thin films and coatings. The mineral can be yellow, burnt orange, brown or black in color. [5] Shigaite occurs in metamorphosed deposits of manganese ore [5] and is the Mn2+ analogue of motukoreaite. [6]
Shigaite consists of oxycation sheets of [AlMn2+2(OH)61+ intercalated with oxyanion sheets of [Na(H2O)6{H2O}6(SO4)23−. Linkage between the sheets and within the oxyanion sheet results largely through hydrogen bonding. [6]
Shigaite was discovered in 1985 in the Ioi Mine, [a] Shiga Prefecture, Japan. [3] The original study, published in the journal Neues Jahrbuch für Mineralogie, Monatshefte, [1] identified the formula as Al4Mn7(SO4)2(OH)22·8H2O. [7] The formula was significantly revised in 1996 using a sample from the N'Chwaning Mine, South Africa. [6] Sodium, discovered to be a component of shigaite, was not identified in the original study. However, an unidentified volatile had been noted that presumably was a sodium-containing complex. [8]
As of 2012 [update], shigaite is known from the following sites: [3]
- Iron Monarch open cut, South Australia, Australia
- Poudrette quarry, Quebec, Canada
- Ioi mine, Shiga Prefecture, Japan
- Wessels Mine, Northern Cape Province, South Africa
- N'Chwaning Mine, Northern Cape Province, South Africa
- Homer Mine, Michigan, United States
- Bengal Mine, Michigan, United States
The type material is housed in the National Museum of Natural History in Washington, D.C. as sample 122089. [5]
Shigaite has been found associated with the following minerals: [5]
|
Ioi mine, Japan
|
Wessels Mine, South Africa
|
Iron Monarch, South Australia
|
- ^ a b Nickel, Ernest H. "IMA/CNMNC List of Mineral Names" (PDF). Materials Data, Inc. Retrieved May 6, 2012.
- ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode: 2021MinM...85..291W. doi: 10.1180/mgm.2021.43. S2CID 235729616.
- ^ a b c d e f g h i j "Shigaite". Mindat. Retrieved April 20, 2012.
- ^ a b c d "Shigaite Mineral Data". Webmineral. Retrieved May 20, 2012.
- ^ a b c d e f g h i j k l "Shigaite" (PDF). Handbook of Mineralogy. Mineral Data Publishing. Retrieved April 20, 2012.
- ^ a b c Cooper, p. 91.
- ^ a b Hawthorne, Frank C.; et al. (November–December 1986). "New Mineral Names" (PDF). American Mineralogist. 71 (11 & 12): 1546. Retrieved May 17, 2012.
- ^ Cooper, p. 96.
- Cooper, Mark A.; Hawthorne, Frank C. (February 1996). "The crystal structure of shigaite, (AlMn (super 2+)2 (OH)6)3 (SO4)2 Na(H2O)6 {H2O}6, hydrotalcite-group mineral" (PDF). The Canadian Mineralogist. 34 (1): 91–97. ISSN 0008-4476. Retrieved May 23, 2012.
- Pring, A.; Slade, P. G.; Birch, W. D. (September 1992). "Shigaite from Iron Monarch, South Australia" (PDF). Mineralogical Magazine. 56 (384): 417–419. Bibcode: 1992MinM...56..417P. doi: 10.1180/minmag.1992.056.384.15. S2CID 140697083. Retrieved April 20, 2012.
| Shigaite | |
|---|---|
|
Reddish-brown shigaite crystal (2 cm across) with pink
rhodochrosite from South Africa | |
| General | |
| Category | Sulfate mineral |
|
Formula (repeating unit) | NaAl3(Mn2+)6(SO4)2(OH)18·12H2O [1] |
| IMA symbol | Sga [2] |
| Strunz classification | 7.DD.35 [3] |
| Dana classification | 31.1.2.1 [3] |
| Crystal system | Trigonal |
| Crystal class | Rhombohedral (3) H-M symbol: (3) [3] |
| Space group | R3 [4] |
| Unit cell | a = 9.51 Å, c = 32.83 Å, [3] Z = 3 [5] |
| Identification | |
| Color | Yellow, burnt orange, brown, black [5] |
| Twinning | On {0001} [5] |
| Cleavage | Perfect on {0001} [5] |
| Tenacity | Moderately flexible [5] |
| Mohs scale hardness | 2 [5] |
| Luster | Vitreous to dull [3] |
| Streak | Very pale yellow to white [5] |
| Diaphaneity | Transparent [3] |
| Specific gravity | 2.32 [4] |
| Optical properties | Uniaxial (−) [3] |
| Refractive index | n = 1.546 [4] |
| Pleochroism | Distinct; O = yellow; E = very pale yellow [5] |
| Ultraviolet fluorescence | Non-fluorescent [4] |
Shigaite is a mineral with formula NaAl3(Mn2+)6(SO4)2(OH)18·12H2O that typically occurs as small, hexagonal crystals or thin coatings. It is named for Shiga Prefecture, Japan, where it was discovered in 1985. [3] The formula was significantly revised in 1996, identifying sodium as a previously unknown constituent.
Shigaite occurs as hexagonal tabular crystals up to 2 cm (0.79 in) in size or as thin films and coatings. The mineral can be yellow, burnt orange, brown or black in color. [5] Shigaite occurs in metamorphosed deposits of manganese ore [5] and is the Mn2+ analogue of motukoreaite. [6]
Shigaite consists of oxycation sheets of [AlMn2+2(OH)61+ intercalated with oxyanion sheets of [Na(H2O)6{H2O}6(SO4)23−. Linkage between the sheets and within the oxyanion sheet results largely through hydrogen bonding. [6]
Shigaite was discovered in 1985 in the Ioi Mine, [a] Shiga Prefecture, Japan. [3] The original study, published in the journal Neues Jahrbuch für Mineralogie, Monatshefte, [1] identified the formula as Al4Mn7(SO4)2(OH)22·8H2O. [7] The formula was significantly revised in 1996 using a sample from the N'Chwaning Mine, South Africa. [6] Sodium, discovered to be a component of shigaite, was not identified in the original study. However, an unidentified volatile had been noted that presumably was a sodium-containing complex. [8]
As of 2012 [update], shigaite is known from the following sites: [3]
- Iron Monarch open cut, South Australia, Australia
- Poudrette quarry, Quebec, Canada
- Ioi mine, Shiga Prefecture, Japan
- Wessels Mine, Northern Cape Province, South Africa
- N'Chwaning Mine, Northern Cape Province, South Africa
- Homer Mine, Michigan, United States
- Bengal Mine, Michigan, United States
The type material is housed in the National Museum of Natural History in Washington, D.C. as sample 122089. [5]
Shigaite has been found associated with the following minerals: [5]
|
Ioi mine, Japan
|
Wessels Mine, South Africa
|
Iron Monarch, South Australia
|
- ^ a b Nickel, Ernest H. "IMA/CNMNC List of Mineral Names" (PDF). Materials Data, Inc. Retrieved May 6, 2012.
- ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode: 2021MinM...85..291W. doi: 10.1180/mgm.2021.43. S2CID 235729616.
- ^ a b c d e f g h i j "Shigaite". Mindat. Retrieved April 20, 2012.
- ^ a b c d "Shigaite Mineral Data". Webmineral. Retrieved May 20, 2012.
- ^ a b c d e f g h i j k l "Shigaite" (PDF). Handbook of Mineralogy. Mineral Data Publishing. Retrieved April 20, 2012.
- ^ a b c Cooper, p. 91.
- ^ a b Hawthorne, Frank C.; et al. (November–December 1986). "New Mineral Names" (PDF). American Mineralogist. 71 (11 & 12): 1546. Retrieved May 17, 2012.
- ^ Cooper, p. 96.
- Cooper, Mark A.; Hawthorne, Frank C. (February 1996). "The crystal structure of shigaite, (AlMn (super 2+)2 (OH)6)3 (SO4)2 Na(H2O)6 {H2O}6, hydrotalcite-group mineral" (PDF). The Canadian Mineralogist. 34 (1): 91–97. ISSN 0008-4476. Retrieved May 23, 2012.
- Pring, A.; Slade, P. G.; Birch, W. D. (September 1992). "Shigaite from Iron Monarch, South Australia" (PDF). Mineralogical Magazine. 56 (384): 417–419. Bibcode: 1992MinM...56..417P. doi: 10.1180/minmag.1992.056.384.15. S2CID 140697083. Retrieved April 20, 2012.