Johannsenite
| Johannsenite | |
|---|---|
 |
|
| General and classification | |
| chemical formula | CaMn 2+ Si 2 O 6 |
|
Mineral class (and possibly department) |
Silicates and Germanates |
|
System no. to Strunz and to Dana |
9.DA.15 ( 8th edition : VIII / F.01) 65.01.3a.04 |
| Similar minerals | Diopside and hedenbergite |
| Crystallographic Data | |
| Crystal system | Monoclinic |
| Crystal class ; symbol | monoclinic prismatic; 2 / m |
| Space group | C 2 / c (No. 15) |
| Lattice parameters |
a = 9.987 Å ; b = 9.156 Å; c = 5.293 Å β = 105.29 ° |
| Formula units | Z = 4 |
| Twinning | often to {110} |
| Physical Properties | |
| Mohs hardness | 6th |
| Density (g / cm 3 ) | measured: 3.27-3.54; calculated: 3.52 |
| Cleavage | good at {110}, (110)? (1 1 0) ~ 87 °, partially at {100}, {001} and {010} |
| Break ; Tenacity | brittle |
| colour | carnation brown, green, black, blue, gray |
| Line color | greenish-gray |
| transparency | translucent to opaque |
| shine | not known |
| Crystal optics | |
| Refractive indices |
n α = 1.699-1.710 n β = 1.710-1.719 n γ = 1.725-1.738 |
| Optical character | biaxial positive |
| Axis angle | 2V = 58 ° -72 ° |
| Other properties | |
| Chemical behavior | soluble in hot hydrochloric acid |
Johannsenite is a rare mineral from the mineral class of the silicates and Germanates . It crystallizes in the monoclinic crystal system with the chemical composition CaMn 2+ Si 2 O 6 .
Johannsenite forms primatic crystals up to 10 cm in size . It also forms columnar, radial or spherulitic mineral aggregates .
Etymology and history
The mineral was discovered by Waldemar Theodor Schaller in 1932. He first mentioned it in a short paper in December 1932 at a conference of the Mineralogical Society of America . He was only saying something about a manganese pyroxene at the time . Before it was first described in the American Mineralogist published by the Mineralogical Society of America, the mineral had already been found at other sites. However, this description did not follow until 1938. In this complete description, Schaller named the mineral after the mineralogist and petrographer Albert Johannsen (1871–1962). The type locality is the "Franklin Mine" in Franklin , Sussex County in the state of New Jersey in the United States of America .
The type material is kept in the National Museum of Natural History in Washington, DC (USA).
classification
In the structural classification of the International Mineralogical Association (IMA) Johannsenite belongs together with pyroxene , Burnettit , Davisit , diopside , Essenit , Grossmanit , Hedenbergit , Kushiroit , Petedunnit and Tissintit to Kalziumpyroxenen (Ca pyroxene) in pyroxene .
Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the Johannsenite belonged to the mineral class of "silicates and germanates" and there to the department of " chain silicates and band silicates (inosilicates)", where it together with aegirine , augite, diopside , Esseneit, Hedenbergit, Jadeit , Jervisit , kanoite , clino-enstatite , Klinoferrosilit , Kosmochlor , Namansilit , Natalyit , omphacite , Petedunnit, pigeonite and spodumene the group of "clinopyroxene" with the system number VIII / F.01 within the head group " pyroxene formed".
The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the IMA, also classifies the Johannsenite under the category of "chain and band silicates (inosilicates)". However, this is further subdivided according to the nature of the silicate chains, so that the mineral is classified according to its composition in the sub-section “Chain and band silicates with 2-periodic single chains Si 2 O 6 ; Pyroxene family "can be found where it is with augite, davisite, diopside, esseneit, hedenbergite, kushiroite and petedunnite in the unnamed subgroup" Ca-Klinopyroxene, diopside group "with the system number 9.DA.15.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns Johannsenite to the class of “silicates and germanates” and there in the section “simple unbranched chains, W = 1 with chains P = 2”. Here it is in the " C2 / c Klinopyroxene (Ca-Klinopyroxene) " with the system no. 65.01.3a to be found, together with diopside, hederbergite, augite, petedunnite, esseneit and davisite.
Crystal structure
Johannsenite crystallizes isotypically to diopside and hedenbergite monoclinically in the space group C 2 / c (space group no. 15) with the lattice parameters a = 9.987 Å ; b = 9.156 Å; c = 5.293 Å and β = 105.29 ° as well as four formula units per unit cell .
Education and Locations
Johannsenite forms in metasomatically overprinted limestones and manganese-containing skarns , as well as in quartz and calcite veins in rhyolite . Often in paragenesis with rhodonite and manganese oxides .
Currently (2015) 66 sites are known of the mineral.
In Germany only one site is known, it is in Lower Saxony in the Harz Mountains , in the town of Sankt Andreasberg .
There are other sites in Australia , Bulgaria , China , France , Indonesia , Italy , Japan , Canada , Mexico , Norway , Peru , Macedonia , Romania , Russia , South Africa , Spain , Sweden , Tajikistan , the United Kingdom and the United States of America .
See also
literature
- RF Freed, Donald R. Peacor: Refinement of the crytal structure of johannsenite . In: American Mineralogist . tape 52 . Mineralogical Society of America, 1967, pp. 709-720 . ( PDF )
Web links
- Web mineral: Johannsenite
- Johannsenite - Database-of-Raman-spectroscopy
- Johannsenite - American-Mineralogist-Crystal-Structure-Database
Individual evidence
- ↑ a b c d e f g h Johannsenite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 66 , 9 kB )
- ↑ Mineral Atlas: Johannsenite
- ↑ a b c d e Mindat - Locations for Johannsenite (English)
- ^ A b Waldemar Theodor Schaller: Johannsenite, a new manganese pyroxene . In: American Mineralogist . tape September 23 , 1938, p. 575-582 . ( PDF )
- ↑ Subcommite on Pyroxenes, CNMMN; Nobuo Morimoto: Nomenclature of Pyroxenes . In: The Canadian Mineralogist . tape 27 , 1989, pp. 143–156 ( mineralogicalassociation.ca [PDF; 1.6 MB ; accessed on November 11, 2018]).