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About KotoiteHide

Bundjirô Kotô
Colorless; colorless in transmitted light
Vitreous, Sub-Vitreous
Specific Gravity:
Crystal System:
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.
Isostructural with:
Type locality has white to colorless masses in dolomite.

Classification of KotoiteHide

Approved, 'Grandfathered' (first described prior to 1959)
First Published:

A : Monoborates
A : BO3, without additional anions; 1(D).

3 : AmBn[XO3]p

9 : Borates
2 : Borates of Be and Mg

Physical Properties of KotoiteHide

Vitreous, Sub-Vitreous
Transparent, Translucent
Generally low lustered granular
Colorless; colorless in transmitted light
6½ on Mohs scale
On {110}
On {101}. Also exhibits translation gliding.
3.10 g/cm3 (Measured)    3.06 g/cm3 (Calculated)
D = 3.06-3.09

Optical Data of KotoiteHide

Biaxial (+)
RI values:
nα = 1.652 nβ = 1.653 nγ = 1.673
Measured: 21° , Calculated: 26°
Max Birefringence:
δ = 0.021
Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.
Surface Relief:
r > v weak
Optical Extinction:

Chemical Properties of KotoiteHide

IMA Formula:

Crystallography of KotoiteHide

Crystal System:
Class (H-M):
mmm (2/m 2/m 2/m) - Dipyramidal
Space Group:
Cell Parameters:
a = 5.401 Å, b = 8.422 Å, c = 4.507 Å
a:b:c = 0.641 : 1 : 0.535
Unit Cell V:
205.01 ų (Calculated from Unit Cell)
Massive, granular.
On {101} as the twin and composition plane, polysynthetic.

X-Ray Powder DiffractionHide

Powder Diffraction Data:
3.46 (20)
2.67 (100)
2.32 (30)
2.23 (70)
2.18 (80)
1.73 (50)
1.67 (50)
1.52 (30)

Type Occurrence of KotoiteHide

General Appearance of Type Material:
Colorless massive to elongated grains to several mm
Geological Setting of Type Material:
Contact metamorphic zone of a granitic intrusion into dolomite.
Associated Minerals at Type Locality:

Other Language Names for KotoiteHide

Simplified Chinese:粒镁硼石

Common AssociatesHide

Associated Minerals Based on Photo Data:
Ludwigite3 photos of Kotoite associated with Ludwigite on mindat.org.
Szaibélyite3 photos of Kotoite associated with Szaibélyite on mindat.org.
Pertsevite-(OH)2 photos of Kotoite associated with Pertsevite-(OH) on mindat.org.
Pertsevite-(F)2 photos of Kotoite associated with Pertsevite-(F) on mindat.org.

Related Minerals - Nickel-Strunz GroupingHide

6.AA.05SassoliteH3BO3Tric. 1 : P1
6.AA.15NordenskiöldineCaSn4+[BO3]2Trig. 3 : R3
6.AA.15TusioniteMn2+Sn4+[BO3]2Trig. 3 : R3

Related Minerals - Dana Grouping (8th Ed.)Hide,Mg)3[BO3]2Orth.

Related Minerals - Hey's Chemical Index of Minerals GroupingHide

9.2.1HambergiteBe2(BO3)(OH)Orth. mmm (2/m 2/m 2/m) : Pbca
9.2.6AksaiteMg[B6O7(OH)6] · 2H2OOrth. mmm (2/m 2/m 2/m) : Pbca
9.2.7WightmaniteMg5(BO3)O(OH)5 · 2H2OMon.
9.2.8PinnoiteMg[B2O(OH)6]Tet. 4/m : P42/m
9.2.9KurnakoviteMgB3O3(OH)5 · 5H2OTric. 1 : P1
9.2.10HalurgiteMg2[B4O7]2 · 5H2OMon.
9.2.11InderiteMgB3O3(OH)5 · 5H2OMon. 2/m : P21/b
9.2.12HungchaoiteMg(B4O7) · 9H2OTric. 1
9.2.13AdmontiteMgB6O10 · 7H2OMon.
9.2.14McallisteriteMg2[B6O7(OH)6]2 · 9H2OTrig. 3m (3 2/m) : R3c
9.2.15RivadaviteNa6Mg[B6O7(OH)6]4 · 10H2OMon. 2/m : P21/m
9.2.16KaliboriteKMg2H[B6O8(OH)5]2(H2O)4Mon. 2/m : B2/b
9.2.17IquiqueiteK3Na4Mg(CrO4)B24O39(OH) · 12H2OHex.

Fluorescence of KotoiteHide

Not fluorescent

Other InformationHide

Thermal Behaviour:
Melting Point = ~ 1340° C.
Readily soluble in warm HCl or H2SO4.

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 petrologyHide

An essential component of rock names highlighted in red, an accessory component in rock names highlighted in green.

References for KotoiteHide

Reference List:
Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Mallard (1887) Comptes rendu de l’Académie des sciences de Paris: 105: 1260 (artificial crystals).
Mallard (1887) Annales des mines: 12(8): 427 (artificial crystals).
Mallard (1889) Zeitschrift für Kristallographie, Mineralogie und Petrographie, Leipzig: 15: 650 (artificial crystals).
Watanabe, T. (1939) Kotoit, ein neues gesteinsbildenes magnesiumborat. Mineralogische und petrographische Mitteilungen, Vienna: 50: 441-463.
Watanabe, T. (1939) Mineralogische und petrographische Mitteilungen, Vienna: 51: 162.
Watanabe, T. (1939) Kotoit, Mg3B20s, ein neues gesteinsbildendes Mineral. Fortschritte der Mineralogie, Kristallographie und Petrographie: 23: ?.
Foshag, W.F. (1939) New mineral names. American Mineralogist: 24: 406-406.
Palache, C., Berman, H., Frondel, C. (1951) The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, Yale University 1837-1892, Volume II. John Wiley and Sons, Inc., New York, 7th edition, revised and enlarged: 328-329.
Watanabe, T., Kato, A. (1956) On kotoite from the Neichi mine, Miyako city, Iwate prefecture (abstr.). Journal of the Geological Society of Japan: 62: 394.
Watanabe, T. (1963) Kotoite, Mg3(BO3)2, from the Neichi mine, Iwate Prefecture, Japan. Proceedings of the Japan Academy: 39(3): 164-169.
Effenberger, H., Pertlik, F. (1984) Verfeinerung der kristallstrukturen der isotypen verbindungen M3(BO3)2 mit M=Mg, Co und Ni (strukturtyp: kotoit). Zeitschrift für Kristallographie: 166: 129-140.
Grew, E.S., Anovitz, L.M. (1996) BORON: Mineralogy, Petrology and Geochemistry, second edition, as revised (2002).

Internet Links for KotoiteHide

Localities for KotoiteHide

This map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.

Locality ListHide

- This locality has map coordinates listed. - This locality has estimated coordinates. ⓘ - Click for 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 (eg from pseudomorphs.)

All localities listed without proper references should be considered as questionable.
  • Guangdong
    • Heyuan
      • Lianping Co.
Anthony, J.W. et al.: Handbook of Mineralogy
  • Hunan
    • Hengyang
      • Changning Co.
        • Dayishan Sn-polymetallic ore field
Yang Guangming, Peng Zhizhong, and Pan Zhaolu (1985): Acta Mineralogica Sinica 5(2), 97-101; Aleksandrov, S.M. (1998): Geochemistry of skarn and ore formation in dolomites. VSP (Utrecht, Tokyo), 300 pp.
  • Occitanie
    • Pyrénées-Orientales
      • Prats-de-Mollo-la Preste (Prats de Molló-la Presta)
Aleksandrov, S.M. and Troneva, M.A. (2011). Genesis and composition of endogenous borates in the skarns of the Eastern and Centran Pyrenees. Geochemistry International, 49, 849-862.
  • Piedmont
    • Torino Province
      • Canavese District
        • Léssolo
          • Cálea
Gramaccioli, C. M. (1978): Die Mineralien der Alpen. 2 Bände, Franckh'sche Verlagshandlung, Stuttgart, Germany, 503 pp.
  • Iwate
    • Miyako City
Dr. Matsuo Nambu collection (curated at Geological Survey of Japan)
      • Kamineichi
Watanabe et al (1963) Kotoite, Mg3(BO3)2, from the Neichi mine, Iwate prefecture, Japan. Proceedings of the Japan Academy, series B, 39, 164-169.; Masutomi Museum specimens (Kyoto); Aleksandrov, S. M., & Troneva, M. A. (2012). Genesis and composition of borates in the metasomatically altered dolomitic, rhodochrosite, and calcareous marbles of Japan. Geochemistry International, 50(11), 885-898.
North Korea
  • North Hwanghae Province
    • Suan-gun
Tschermaks Min.Petr.Mitt.(1939) 50, 441-463; Dana 7:II::323,370,376.
Watanabe, T. : Boron mineral resources in Korea (in: Geology and Mineral Resources of the Far East, University of Tokyo Press, 1969)
Tschermaks Min. Petr. Mitt. (1939): 50: 441-463; Palache, C., Berman, H., & Frondel, C. (1951), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, Yale University 1837-1892, Volume II: 323, 328, 370,376.
Watanabe, T. : Boron mineral resources in Korea (in: Geology and Mineral Resources of the Far East, University of Tokyo Press, 1969)
  • Bihor
    • Nucet
Ş. Marincea: "Suanite in two boron-bearing magnesian skarns from Romania: data on a longtime ignored mineral species", Neues Jahrbuch für Mineralogie - Abhandlungen 182:183-192 (2006)
Shimizu, M., Kato, A., Cioflica, G., Lupulescu, M., Shimizu, M. (1998): Friedrichite from Băița Bihor, Romania. Canadian Mineralogist 36, 861-868.
Ş. Marincea: "Suanite in two boron-bearing magnesian skarns from Romania: data on a longtime ignored mineral species", Neues Jahrbuch für Mineralogie - Abhandlungen 182:183-192 (2006)
  • Caraş-Severin
    • Banat Mts
Aleksandrov, S.M. (2007): Endogeneous transformation of kotoite in calciphyres at magnesian-skarn deposits of boron. Geochem. Internat., 45, 666-684.
  • Khabarovsk Krai
    • Dzhugdzhur Ridge
Galuskina, I. O., Kadiyski, M., Armbruster, T., Galuskin, E. V., Pertsev, N. N., Dzierzanowski, P., & Wrzalik, R. (2008). A new natural phase in the system Mg2SiO4Mg2BO3FMg2BO3 (OH): composition, paragenesis and structure of OH-dominant pertsevite. European Journal of Mineralogy, 20(5), 951-964.
  • Republic of Karelia
    • Ladoga Region
Ivashchenko, V. I., Valkama, M., Sundblad, K., Golubev, A. I., & Alekseev, V. Y. (2011, September). New data on mineralogy and metallogeny of scarns in the Pitkyaranta ore region. In Doklady Earth Sciences (Vol. 440, No. 1, pp. 1307-1311). SP MAIK Nauka/Interperiodica; Aleksandrov, S. M., & Troneva, M. A. (2009). Composition and genesis of endogenous borates from the Pitkáranta ore field, Karelia. Geochemistry International, 47(9), 914-929.; Ivashchenko, V. I., & Lavrov, О. В. (2006) Ore Deposits and Occurrences in the North Ladoga Region, Southwest Karelia. in Ore Deposits And Occurrences In The North Ladoga Region, Southwest Karelia Field Trip Guidebook. Understanding the genesis of ore deposits to meet the demands of the 21st century 12th Quadrennial IAGOD Symposium 2006. Moscow. P.41-64.
  • Sakha Republic (Yakutia)
[World of Stones 12:49]
    • Polar Yakutia
      • Dogdo River Basin
        • Tas-Khayakhtakh Range
Rudnev, V.V., Chukanov, N.V., Nechelyustov, G.N., Yamnova, N.A. (2007): Hydroxylborite, Mg3(BO3)(OH)3, a new mineral, and the isomorphous fluoborite-hydroxylborite series. Proceedings of the Russian Mineralogical Society, 136(1), 69-82.; Aleksandrov, S.M. (1998): Geochemistry of skarn and ore formation in dolomites. VSP (Utrecht, Tokyo), 300 pp.; Seltmann, R., Soloviev, S., Shatov, V., Pirajno, F., Naumov, E., & Cherkasov, S. (2010). Metallogeny of Siberia: tectonic, geologic and metallogenic settings of selected significant deposits*. Australian Journal of Earth Sciences, 57(6), 655-706
            • Izvestkovyi Stream
E. Galuskin and N.N. Pertsev analytical data; Galuskina I.O., Kadiyski M., Armbruster T., Galuskin E.V., Pertsev N.N., Dzierzanowski P., Wrzalik R. (2008) A new natural phase in the system Mg2SiO4-Mg2BO3F-Mg2BO3(OH): composition, paragenesis and structure of OH-dominant pertsevite, - Eur. J. Mineral., 20, p. 951-964.
Pavel M. Kartashov data
    • Verkhoyansk
      • Yana River Basin
        • Dogdo river
W. Schreyer et al. (2003) Eur. Journ. Mineral. 15, 1007-1018
  • Alaska
    • Nome Borough
      • Seward Peninsula
Aleksandrov, S.M. (1974b) Geochemical features of endogeneous borate mineralization in Italy. Geokhimiya, 5, 763-772 (in Russian. English translation::Geochemistry International, April, 1974, Vol. 10, pp. 987-996).
  • Washington
    • Snohomish Co.
      • Darrington
        • Jumbo Mountain
Minerals of Washington, Bart Cannon, 1975; Aleksandrov, S. M. (2005). Genesis and Composition of Borate and Sulfide Mineralization in the Mount Jumbo Dunite, Snohomish County, Washington, United States. Geochemistry International, 43(3), 277-289.
Mineral and/or Locality  
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