Hutcheonite
| Hutcheonite | |
|---|---|
| General and classification | |
| other names |
IMA 2013-029 |
| chemical formula | Ca 3 Ti 2 Al 2 SiO 12 |
|
Mineral class (and possibly department) |
Silicates and Germanates |
| Crystallographic Data | |
| Crystal system | cubic |
| Crystal class ; symbol | cubic hexakisoctahedral; 4 / m 3 2 / m |
| Space group | Ia 3 d (No. 230) |
| Lattice parameters | a = 11.843 Å |
| Formula units | Z = 8 |
| Physical Properties | |
| Mohs hardness | not determined |
| Density (g / cm 3 ) | calculated: 3.86 |
| Cleavage | not determined |
| Break ; Tenacity | not determined |
| colour | not determined |
| Line color | not determined |
| transparency | not determined |
| shine | not determined |
| Crystal optics | |
| Refractive index | n = not determined |
| Birefringence | δ = not determined |
The mineral hutcheonite is a very rare silicate from the upper group of garnets with the idealized chemical composition Ca 3 Ti 2 Al 2 SiO 12 . It crystallizes in the cubic crystal system with the structure of garnet and is found in the form of crystals a few µm in size in calcium-aluminum-rich inclusions (CAI: calcium aluminum inclusion) in the Allende meteorites .
Except in its type locality , the Allende meteorite, Pueblito de Allende, Chihuahua , Mexico , so far (2017) Hutcheonite-rich garnet has only been detected in calcium silicate rock inclusions of the gabbro in the Harz , Radautal Germany .
Etymology and history
In 1978 Koritnig and his colleagues examined grenades from a lime silicate horn rock in the Bärenstein quarry in the Radau valley (Harz), which had been described in 1903 by J. Fromme and in 1928 by Georg Frebold . These aluminum-rich schorlomite-moromotoite-grossular mixed crystals are in the range of hutcheonite with their composition, but were not regarded as a new mineral.
On February 8, 1969, a meteorite fell in northern Mexico and was named after the place whose post office he barely spared, Pueblito de Allende. This Allende meteorite, a carbonaceous CV3 chondrite , is one of the best studied meteorites worldwide and is the type locality of several minerals. In 2013, Chi Ma and Alexander N. Krot discovered a new species of garnet in it, which they named after the physicist and cosmochemist Ian D. Hutcheon of the Lawrence Livermore National Laboratory , in recognition of his numerous contributions to the chemistry of the cosmos and meteorites.
classification
The current classification of the International Mineralogical Association (IMA) counts the Hutcheonite to the garnet upper group, where together with kimzeyite , irinarassite , schorlomite , kerimasite and toturite it forms the schorlomite group with 10 positive charges on the tetrahedral coordinated lattice position.
The outdated, but still in use 8th edition of the mineral classification according to Strunz does not yet list the Hutcheonite. He would, together with almandine Andradite , Calderit , Goldmanit , Grossular , Henritermierit , Hibschite , Holtstamit , Hydrougrandit, katoite , Knorringit , majorite , Morimotoit , pyrope , Schorlomit, Spessartin , Uwarowit , wadalite and Yamatoit (discredited because identical to Momoiit ) for " Garnet group "with the system no. VIII / A.08 in the section of " Island Silicates (Nesosilicates)".
Even the 9th edition of Strunz's mineral systematics, which has been in effect since 2001 , does not yet know the Hutcheonite. Here he would also use the "garnet group" with the system no. 9.AD.25 within the division of "Island Silicates (Nesosilicates)". This is further subdivided according to the possible presence of further anions and the coordination of the cations involved , so that the mineral is classified according to its composition in the subsection “Island silicates without additional anions; Cations in octahedral [6] and usually greater coordination ”would be found. The garnets irinarassite, kerimasite, toturite, menzerite (Y) and eringaite described after 2001 would also have been sorted into the garnet group.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , would classify the Hutcheonite in the department of "island silicate minerals ". Here it would be together with kimzeyite, schorlomite and morimotoite in the "garnet group (schorlomite-kimzeyite series)" with the system no. 51.04.03c within the subsection “ Island silicates: SiO 4 groups only with cations in [6] and> [6] coordination ”.
Chemism
Hutcheonit is the Al-analog of Schorlomit and forms complex solid solutions especially with Kimzeyit, Schorlomit, Grossular and Morimotoit . The measured composition from the type locality is
- [X] Ca 2.99 [Y] (Ti 4+ 1.53 Mg 0.25 Al 0.17 Fe 2+ 0.05 V 3+ 0.03 ) [Z] (Si 1.68 Al 1.32 ) O 12 ,
where [X], [Y] and [Z] indicate the positions in the garnet structure.
This corresponds to a mixture of 66% Hutcheonite (Ca 3 Ti 2 Al 2 SiO 12 ) with 22% Morimotoite-Mg (Ca 3 Ti (Mg, Fe) 2+ Si 3 O 12 ) according to the exchange reaction
- [Y] Ti 4+ + 2 [Z] Al 3+ = [Y] (Mg, Fe) 2+ + 2 [Z] Si 4+ ,
and 12% grossular (Ca 3 (Al, V 3+ ) 2 Si 3 O 12 ) according to the exchange reaction
- [Y] Ti 4+ + [Z] Al 3+ = [Y] (Al, V 3+ ) + [Z] Si 4+ .
Crystal structure
Hutcheonite crystallizes with cubic symmetry in the space group Ia 3 d (space group no. 230) with 8 formula units per unit cell . The natural mixed crystal from the type locality has the lattice parameter a = 11.843 Å .
The structure is that of garnet . Calcium (Ca 2+ ) occupies the dodecahedral X positions surrounded by 8 oxygen ions, titanium (Ti 4+ ) the octahedral Y position surrounded by 6 oxygen ions and the tetrahedral Z position surrounded by 4 oxygen ions is aluminum (Al 3+ ) and silicon (Si 4+ ) occupied.
Education and Locations
The type locality of Hutcheonite is the Allende meteorite , a carbonaceous CV3 chondrite from Pueblito de Allende, Chihuahua , Mexico . Here hutcheonite occurs in calcium-aluminum-rich inclusions (CAI). Accompanying minerals are monticellite , grossular , wadalite and adrianite . It is believed that in itself Hutcheonit meteorites in the conversion of melilite , perovskite and Ti-Al diopside by iron alkali - halogen flood - fluids forms.
There will be a formation 3–4 * 10 9 years after the formation of CAI at temperatures below 600 ° C z. B. about the reaction
- 3 Melilite + Al, Ti-Diopside + Cl (aq) + 6.12 H 2 O (l) = 0.17 Adrianite + Hutcheonite + 1.5 Monticellite + 0.88 Grossular + 0.5 Kushiroite + 1.39 Approx (aq) + 0.05 Al (aq) + 0.04 SiO 2 (aq) + 6.12 H 2 (g)
accepted.
See also
Web links
- Mineral Atlas: Hutcheonite (Wiki)
- Mindat - Hutcheonite (English)
Individual evidence
- ↑ a b c d e f g h i j k Chi Ma and Alexander N. Krot: Hutcheonite, Ca3Ti2 (SiAl2) O12, a new garnet mineral from the Allende 2 meteorite: An alteration phase in a Ca-Al-rich inclusion . In: American Mineralogist . tape 99 , no. 4 , April 2014, p. 667–670 ( minsocam.org [PDF; 2.8 MB ; accessed on October 3, 2017]).
- ↑ a b S. Koritnig, H. Rösch, A. Schneider, F. Seifert: The titanium zirconium garnet from the calcium silicate rock inclusions of the gabbro in the Radautal, Harz, Federal Republic of Germany . In: TMPM Tschermaks Mineralogische und Petrographische Mitteilungen . tape 25 , no. 4 , December 1978, p. 305-313 , doi : 10.1007 / BF01180234 .
- ^ Edward S. Grew, Andrew J. Locock, Stuart J. Mills, Irina O. Galuskina, Evgeny V. Galuskin and Ulf Hålenius: IMA Report - Nomenclature of the garnet supergroup . In: American Mineralogist . tape 98 , 2013, p. 785–811 ( main.jp [PDF; 2,3 MB ; accessed on April 29, 2020]).
- ↑ a b Chi Ma and Alexander N. Krot: Adrianite, Ca12 (Al4Mg3Si7) O32Cl6, a new Cl-rich silicate mineral from the Allende meteorite: An alteration phase in a Ca-Al-rich inclusion. In: American Mineralogist . In Press, 2018 ( minsocam.org [PDF; 1.5 MB ; accessed on July 22, 2018]).