Kotoite
A valid IMA mineral species - grandfathered
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About Kotoite
Bundjirô Kotô
Formula:
Mg3[BO3]2
Colour:
Colorless; colorless in transmitted light
Lustre:
Vitreous, Sub-Vitreous
Hardness:
6½
Specific Gravity:
3.10
Crystal System:
Orthorhombic
Name:
Named in honor of Bundjirô Kotô (小藤文次郎) (8 April 1856, Iwami Province (now Shimane Prefecture) Japan - 8 March 1935, Tokyo, Japan), geologist and petrographer. He was a Professor of Geology, Science College, Imperial University of Tokyo, who first described the ore deposits of the type locality of Hol Kol.
Type Locality:
Isostructural with:
Type locality has white to colorless masses in dolomite.
Unique Identifiers
Mindat ID:
2262
Long-form identifier:
mindat:1:1:2262:6
GUID
(UUID V4):
(UUID V4):
df31da50-b223-465c-a1ba-1c71ad92d2cc
IMA Classification of Kotoite
Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
Mg3(BO3)2
First published:
1939
Classification of Kotoite
6.AA.35
6 : BORATES
A : Monoborates
A : BO3, without additional anions; 1(D).
6 : BORATES
A : Monoborates
A : BO3, without additional anions; 1(D).
24.3.2.1
24 : ANHYDROUS BORATES
3 : AmBn[XO3]p
24 : ANHYDROUS BORATES
3 : AmBn[XO3]p
9.2.3
9 : Borates
2 : Borates of Be and Mg
9 : Borates
2 : Borates of Be and Mg
Mineral Symbols
As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.
| Symbol | Source | Reference |
|---|---|---|
| Ko | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
Physical Properties of Kotoite
Vitreous, Sub-Vitreous
Transparency:
Transparent, Translucent
Comment:
Generally low lustered granular
Colour:
Colorless; colorless in transmitted light
Streak:
White
Hardness:
6½ on Mohs scale
Tenacity:
Brittle
Cleavage:
Perfect
On {110}
On {110}
Parting:
On {101}. Also exhibits translation gliding.
Density:
3.10 g/cm3 (Measured) 3.06 g/cm3 (Calculated)
Comment:
D = 3.06-3.09
Optical Data of Kotoite
Type:
Biaxial (+)
RI values:
nα = 1.652 nβ = 1.653 nγ = 1.673
2V:
Measured: 21° , Calculated: 26°
Birefringence:
0.021
Max Birefringence:
δ = 0.021
Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.
and does not take into account mineral colouration.
Surface Relief:
Moderate
Dispersion:
r > v weak
Optical Extinction:
Parallel
Pleochroism:
Non-pleochroic
Chemistry of Kotoite
Mindat Formula:
Mg3[BO3]2
Elements listed:
Crystallography of Kotoite
Crystal System:
Orthorhombic
Class (H-M):
mmm (2/m 2/m 2/m) - Dipyramidal
Space Group:
Pnnm
Cell Parameters:
a = 5.401 Å, b = 8.422 Å, c = 4.507 Å
Ratio:
a:b:c = 0.641 : 1 : 0.535
Unit Cell V:
205.01 ų (Calculated from Unit Cell)
Z:
2
Morphology:
Massive, granular.
Twinning:
On {101} as the twin and composition plane, polysynthetic.
Comment:
Pnmn
Crystal Structure
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Data courtesy of the American Mineralogist Crystal Structure Database. Click on an AMCSD ID to view structure
| ID | Species | Reference | Link | Year | Locality | Pressure (GPa) | Temp (K) |
|---|---|---|---|---|---|---|---|
| 0010864 | Kotoite | Effenberger H, Pertlik F (1984) Verfeinerung der kristallstrukturen der isotypen verbindungen M3(BO3)2 mit M=Mg, Co und Ni (strukturtyp: kotoit) Zeitschrift fur Kristallographie 166 129-140 |  | 1984 | synthetic | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 3.46 Å | (20) |
| 2.67 Å | (100) |
| 2.32 Å | (30) |
| 2.23 Å | (70) |
| 2.18 Å | (80) |
| 1.73 Å | (50) |
| 1.67 Å | (50) |
| 1.52 Å | (30) |
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Near-surface Processes | |
| 23 : Subaerial aqueous alteration by non-redox-sensitive fluids (see also #47) |
Type Occurrence of Kotoite
General Appearance of Type Material:
Colorless massive to elongated grains to several mm.
Place of Conservation of Type Material:
The Natural History Museum, London, England, 1938,1286.
Harvard University, Cambridge, Massachusetts, USA, 94750.
National Museum of Natural History (Smithsonian), Washington, D.C., USA, 103502.
Harvard University, Cambridge, Massachusetts, USA, 94750.
National Museum of Natural History (Smithsonian), Washington, D.C., USA, 103502.
Geological Setting of Type Material:
Contact metamorphic zone of a granitic intrusion into dolomite.
Associated Minerals at Type Locality:
Reference:
Watanabe, T. (1939) Kotoit, ein neues gesteinsbildenes magnesiumborat. Mineralogische und petrographische Mitteilungen, Vienna: 50: 441-463.
Other Language Names for Kotoite
Common Associates
Associated Minerals Based on Photo Data:
| 6 photos of Kotoite associated with Ludwigite | Mg2Fe3+(BO3)O2 |
| 4 photos of Kotoite associated with Szaibélyite | MgBO2(OH) |
| 3 photos of Kotoite associated with Clinohumite | Mg9(SiO4)4F2 |
| 2 photos of Kotoite associated with Pertsevite-(OH) | Mg2(BO3)(OH) |
| 2 photos of Kotoite associated with Pertsevite-(F) | Mg2(BO3)(F,OH) |
| 2 photos of Kotoite associated with Dolomite | CaMg(CO3)2 |
| 1 photo of Kotoite associated with Spinel | MgAl2O4 |
Related Minerals - Strunz-mindat Grouping
| 6.AA.05 | Sassolite | H3BO3 |
| 6.AA.15 | Nordenskiöldine | CaSn4+[BO3]2 |
| 6.AA.15 | Tusionite | Mn2+Sn4+[BO3]2 |
| 6.AA.35 | Jimboite | (Mn2+,Mg)3[BO3]2 |
| 6.AA.40 | Takedaite | Ca3[BO3]2 |
Fluorescence of Kotoite
Not fluorescent
Other Information
Thermal Behaviour:
Melting Point = ~ 1340° C.
Notes:
Readily soluble in warm HCl or H2SO4.
Alters to Szaibelyite under hydrothermal conditions.
Alters to Szaibelyite under hydrothermal conditions.
Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.
Kotoite in petrology
An essential component of rock names highlighted in red, an accessory component in rock names highlighted in green.
Internet Links for Kotoite
mindat.org URL:
https://www.mindat.org/min-2262.html
Please feel free to link to this page.
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References for Kotoite
Localities for Kotoite
symbol to view information about a locality.
The Locality List
- This locality has map coordinates listed.
- This locality has estimated coordinates.
ⓘ - 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).
All localities listed without proper references should be considered as questionable.
China | |
| Anthony |
| Yang Guangming et al. (1985) +1 other reference |
France | |
| Aleksandrov et al. (2011) |
Italy | |
| Gramaccioli (1978) +1 other reference |
Japan | |
| Dr. Matsuo Nambu collection (curated at Geological Survey of Japan) |
| Masutomi Museum specimens (Kyoto) +2 other references |
North Korea | |
| Dana 7:II::323 +1 other reference |
| watanabe (in: Geology and Mineral Resources of the Far East, University of Tokyo Press, 1969) +1 other reference | |
| Tschermaks Min. Petr. Mitt. (1939) +2 other references | |
| watanabe (in: Geology and Mineral Resources of the Far East, University of Tokyo Press, 1969) | |
Romania | |
| Ş +1 other reference |
| Shimizu et al. (1998) | |
| Ş +1 other reference | |
| Marincea et al. (2023) | |
| Aleksandrov (2007) |
| Marincea (2000) |
Russia | |
| Galuskina et al. (2008) |
| Shevko et al. (2019, September) |
| Ivashchenko et al. (2006) +2 other references |
| [World of Stones 12:49] | |
| Aleksandrov (1998) +2 other references |
| Galuskin +1 other reference |
| Pavel.M. Kartashov (n.d.) | |
| W. Schreyer et al. (2003) |
Spain | |
| Torres Ruiz +2 other references |
USA | |
| Aleksandrov (1974b) |
| Gillerman (1982) |
| Woodford et al. (2001) |
| Cannon (1975) +1 other reference |
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Băiţa mining district, Nucet, Bihor County, Romania