Itoigawait
| Itoigawait | |
|---|---|
| General and classification | |
| other names |
IMA 1998-034 |
| chemical formula | SrAl 2 [(OH) 2 | Si 2 O 7 ] · H 2 O |
|
Mineral class (and possibly department) |
Silicates and Germanates |
|
System no. to Strunz and to Dana |
9.BE.05 ( 8th edition : VIII / C.10) 02.56.03.05 |
| Crystallographic Data | |
| Crystal system | orthorhombic |
| Crystal class ; symbol | orthorhombic-dipyramidal; 2 / m 2 / m 2 / m |
| Space group | Cmcm (No. 63) |
| Lattice parameters | a = 6.03 Å ; b = 8.94 Å; c = 13.22 Å |
| Formula units | Z = 4 |
| Physical Properties | |
| Mohs hardness | 5 to 5.5 |
| Density (g / cm 3 ) | calculated: 3.3 |
| Cleavage | Well |
| colour | blue, colorless in thin layers |
| Line color | White |
| transparency | transparent |
| shine | Glass gloss |
| Crystal optics | |
| Refractive indices |
n α = 1.664 n β = 1.674 n γ = 1.688 |
| Birefringence | δ = 0.024 |
| Optical character | biaxial positive |
| Axis angle | 2V = 81 ° (calculated) |
Itoigawaite is a very rarely occurring mineral from the mineral class of " silicates and germanates ". It crystallizes in the orthorhombic crystal system with the chemical composition SrAl 2 [(OH) 2 | Si 2 O 7 ] · H 2 O and has so far only been found in the form of microcrystalline mineral aggregates of blue color with white streak color .
Etymology and history
Itoigawait was first discovered in 1996 as a bluish mineral on lavender-colored jadeite on the scree beach Oyashirazu near Itoigawa in Niigata Prefecture on the Japanese island of Honshu .
The mineral was analyzed and described by H. Miyajima, S. Matsubara, R. Miyawaki and K. Ito, who named it Itoigawa after its type locality . The research group submitted their research results and the chosen name to the International Mineralogical Association (IMA) for examination in 1998 . The application received the entry number IMA 1998-034 and in the same year the status as an independent mineral was confirmed. The research results and the recognized name were published in Mineralogical Magazine in December 1999 .
classification
In the meanwhile outdated, but still in use 8th edition of the mineral systematics according to Strunz , the Itoigawaite belonged to the mineral class of "silicates and germanates" and there to the department of " group silicates (sorosilicates)", where together with hennomartinite , ilvaite , lawsonite and noelbensonite it was one formed an independent group.
The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), also assigns Itoigawait to the class of “silicates and germanates” and there to the “group silicates (sorosilicates)” category. This division, however, is further divided by the nature and linkage of silicate groups and the coordination of the involved cations , so that the mineral according to its crystal structure in the subsection "Si 2 O 7 groups with additional anions ; Cations in octahedral [6] and greater coordination ”can be found, where together with hennomartinite, lawsonite and noelbensonite the“ lawsonite group ”with the system no. 9.BE.05 forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the Itoigawait to the class of “silicates and Germanates”, but there in the more finely subdivided division of “group silicates: Si 2 O 7 groups and O, OH, F and H 2 O “a. Here he is together with lawsonite, hennomartinite, ilvaite, noelbensonite and manganilvaite in the "lawsonite-ilvaite group" with the system no. 56.02.03 within the subsection of " Group silicates: Si 2 O 7 groups and O, OH, F and H 2 O with cations in [4] and / or> [4] coordination ".
Crystal structure
Itoigawaite crystallizes orthorhombically in the space group Cmcm (space group no. 63) with the lattice parameters a = 6.03 Å ; b = 8.94 Å and c = 13.22 Å and 4 formula units per unit cell .
Education and Locations
Itoigawait forms together with jadeite in thin veins of serpentinite rocks .
So far (as of 2016) Itoigawait could only be detected at its type locality Oyashirazu and at Wakasa in the Tottori prefecture .
See also
literature
- H. Miyajima, S. Matsubara, R. Miyawaki, K. Ito: Itoigawaite, a new mineral, the Sr analogue of lawsonite, in jadeitite from the Itoigawa-Ohmi district, central Japan. In: Mineralogical Magazine. December 1999, Vol. 63 (6), pp. 909-916. ( PDF; 323 kB )
Web links
Individual evidence
- ↑ a b c d e 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. 574 .
- ↑ Webmineral - Itoigawaite (English)
- ↑ a b c H. Miyajima, S. Matsubara, R. Miyawaki, K. Ito: Itoigawaite, a new mineral, the Sr analogue of lawsonite, in jadeitite from the Itoigawa-Ohmi district, central Japan. In: Mineralogical Magazine. December 1999, Vol. 63 (6), pp. 909-916. ( PDF; 323 kB )
- ↑ a b c d e Mindat - Itoigawaite (English)