Jimboit

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Jimboit
General and classification
other names

IMA 1963-002

chemical formula Mn 3 [BO 3 ] 2
Mineral class
(and possibly department) 		Borates
System no. to Strunz
and to Dana 		6.AA.35 ( 8th edition : V / G.01)
03/24/02/02
Crystallographic Data
Crystal system orthorhombic
Crystal class ; symbol orthorhombic-dipyramidal; 2 / m 2 / m 2 / m
Room group (no.) Pnmn (No. 58)
Lattice parameters a  = 5.66  Å ; b  = 8.74 Å; c  = 4.65 Å
Formula units Z  = 2
Twinning after {101}
Physical Properties
Mohs hardness 5.5
Density (g / cm 3 ) 3.98 to 4.02
Cleavage completely after {110}; Segregation after {101}
colour reddish brown
Line color White
transparency translucent
shine Glass gloss
Crystal optics
Refractive indices n α  = 1.792
n β  = 1.794
n γ  = 1.821
Birefringence δ = 0.029
Optical character biaxial positive
Axis angle 2V = measured: 30 °; calculated: 32 °

Jimboite is a very rarely occurring mineral from the mineral class of " borates ". It crystallizes in the orthorhombic crystal system with the chemical composition Mn 3 [BO 3 ] 2 and develops mostly tabular V-shaped crystals up to about 5 mm in size, but also fine-veined or granular aggregates of reddish-brown color.


Etymology and history

Jimboit was first found in 1963 in the "Kaso Mine" near Kanuma on the Japanese island of Honshū and described by T. Watanabe, A. Kato, T. Matsumoto and J. Ito who used the mineral in honor of Professor Kotora Jimbo (1867–1924 ), the founder of the Mineralogical Institute of the University of Tokyo , named after him.

classification

In the meantime outdated, but still in use 8th edition of the mineral classification by Strunz of Jimboit belonged to common mineral class of " carbonates , nitrates and borates" and then to the Department of "Island borates" where he along with Kotoit and Takedait the "Kotoit Group “With the system no. V / G.01 formed.

Since the complete revision of Strunz's mineral systematics in the 9th edition (2001), the mineral class of carbonates (and relatives) has been redistributed and the borates form a class of their own. The jimboite is accordingly to be found in the mineral class of "borates" and there in the department of "monoborates". This is further subdivided according to the possible presence of further anions in the formula and the structural arrangement of the borate complex. The simply built jimboite is accordingly in the subsection “BO 3 without additional anions; 1 (Δ) ”, which means that the BO 3 triangles are connected in approximately hexagonal layers. Together with Kotoit he forms the unnamed group 6.AA.35 .

In the Dana system of minerals used in the English-speaking world , the carbonates, nitrates and borates form a common mineral class as in the outdated Strunz system. There, however, the jimboite is in the division of “anhydrous borates” and the sub-division “ anhydrous borates with (A) m (B) n [XO 3 ] p ”, where it also forms the unnamed group 24.3.2 together with the kotoite .

Education and Locations

Jimboit formed presumably by metasomatic reactions between boron hydrothermal solutions and Rhodochrosit in banded manganese - deposits . Accompanying minerals in addition to rhodochrosite are also alabandin , chalcopyrite , galaxite , galena , jacobsite , pyrrhotite and tephroit .

So far (status: 2010) Jimboit could only be found at its type locality “Kaso Mine” near Kanuma in the “Fujii mine” near Wakasa in Fukui Prefecture , which is also on Honshū .

Crystal structure

Jimboite crystallizes orthorhombically in the space group Pnmn (space group no. 58) with the lattice parameters a  = 5.66  Å ; b  = 8.74 Å; and c  = 4.65 Å and 2 formula units per unit cell .

See also

literature

Web links

Individual evidence

  1. ↑ a b c d e f Hugo Strunz , Ernest H. Nickel: Strunz Mineralogical Tables . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p.  330 .
  2. ↑ Webmineral - Jimboite (English)
  3. ↑ a b c d Mindat - Jimboite (English)