Grand manite

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Grand manite
General and classification
other names

IMA 2008-052a

chemical formula CaTi 3+ AlSiO 6
Mineral class
(and possibly department) 		Silicates and Germanates
System no. according to Strunz 9.DA.15
Crystallographic Data
Crystal system monoclinic
Crystal class ; symbol monoclinic prismatic; 2 / m
Space group C 2 / c (No. 15)Template: room group / 15
Lattice parameters a  = 9.80 (1)  Å ; b  = 8.85 (1) Å; c  = 5.360 (5) Å
α  = 90 °; β  = 105.62 (10) °°; γ  = 90 °
Formula units Z  = 4
Physical Properties
Mohs hardness not determined
Density (g / cm 3 ) natural: 3.41 (calculated)
Cleavage Please complete!
colour Naturally; light gray - green
Line color Please complete!
transparency transparent
shine not determined
radioactivity -
magnetism -
Crystal optics
Refractive indices n α  = natural: 1.747 (5)
n β  = natural: 1.750 (5)
n γ  = natural: 1.762 (5)
Birefringence δ = 0.015
Pleochroism dark green - red

The mineral grossmanite is a very rare chain silicate from the pyroxene group with the idealized chemical composition CaTi 3+ AlSiO 6 .

Grossmanit crystallizes with monoclinic symmetry and forms colorless to green crystals of a few µm in size.

In an early phase of the formation of our solar system, pyroxene, rich in gross manite, crystallized at high temperatures and extremely reducing conditions during the resublimation of the presolar nebula and was retained in inclusions of meteorites . Type locality is a calcium-aluminum-rich inclusion (CAI) of the Allende meteorite , in which grossmanite occurs together with spinel , gehlenite , perovskite and grossite .

Etymology and history

Chi Ma and George R. Rossman from the California Institute of Technology in Pasadena , California described the Ti 3+ clinopyroxene from 2 inclusions of the Allende meteorite as a new mineral. They named it after the professor of cosmochemistry at the University of Chicago , Lawrence Grossman, in recognition of his fundamental contributions to meteorite research.

classification

In the structural classification of the International Mineralogical Association (IMA) Grossmanit belongs together with pyroxene , Burnettit , Davisit , diopside , Esseneit , Petedunnit , Hedenbergit , Johannsenite , Kushiroit and Tissintit to Kalziumpyroxenen in pyroxene .

The 9th edition of Strunz's mineral systematics , which has been valid since 2001 and has so far been used by the IMA, does not yet list the Grossmanit. It would have been assigned to the class of "silicates and germanates" and there in the department of "chain and band silicates (inosilicates)". This section is further subdivided according to the type of chain formation, so that the mineral is classified according to its structure in the sub-section “Chain and band silicates with 2-periodic single chains Si2O6; Pyroxen-Familie "would be to be found, where together with Augite, Diopside, Esseneite, Petedunnit, Hedenbergit and Johannsenite to the" Ca-Klinopyroxene, Diopsidegruppe "with the system no. 9.DA.15 belonged to.

Even the outdated, but still in use, 8th edition of the mineral classification according to Strunz does not know the Grossmanit. Here it would belong to the mineral class of "silicates and germanates" and there to the department of "chain silicates and band silicates (inosilicates)", where together with aegirine , augite, petedunnite, esseneit, hedenbergite, jadeite , jervisite , johannsenite, kanoite , clinoenstatite , Klinoferrosilit , Kosmochlor , Namansilit , Natalyit , omphacite , pigeonite and spodumene the "pyroxene, clinopyroxene subgroup" with the system no. VIII / F.01 .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , would place the Grossmanit in the class of "silicates and Germanates" and there in the department of "chain silicate minerals". Here it would be together with diopside, hedenbergite, augite, johannsenite, petedunnite, kushiroite and davisite in the group of " C 2 / c clinopyroxene (Ca-clinopyroxene)" with the system no. 65.01.03.8 within the sub-section " Chain Silicates: Simple unbranched chains, W = 1 with chains P = 2 ".

Chemism

Grossmanite with the idealized composition [M2] Ca [M1] Ti 3+ [T] (AlSi) O 6 is the titanium - aluminum analog of diopside ( [M2] Ca [M1] Mg [T] Si 2 O 6 ), where [M2], [M1] and [T] are the positions in the pyroxene structure.

The compositions of the Grossmanit from the type locality is

  • [M2] Ca 1.000 [M1] (Ti 3+ 0.35 Al 3+ 0.18 Sc 3+ 0.01 V 3+ 0.01 Mg 0.25 Ti 4+ 0.19 ) [T] (Si 1 , 07 Al 0.93 ) O 6

Grossmanit contains variable amounts of Ti 4+ , according to the exchange reactions

  • 2 [M1] Ti 3+ = [M1] Mg 2+ + [M1] Ti 4+ or
  • [M1] Ti 3+ + [T] Si 4+ = [M1] Ti 4+ + [T] Al 3+ (Al-Buffonite)

Grossmanite also forms mixed crystals with diopside, kushiroite, davisite and burnettite:

The mixing behavior of diopside-Al-buffonite-kushiroite-grossmanite mixed crystals is complex with miscibility gaps, the position and extent of which is strongly dependent on the Ti 3+ / Ti 4+ ratio.

Crystal structure

Grossmanit crystallizes with monoclinic symmetry in the space group C 2 / c (space group no. 15) with 4 formula units per unit cell . The lattice parameters of the natural  gross manite are a  = 9.80 (1) Å, b  = 8.85 (1) Å, c = 5.36 (5) Å and β = 105.62 (10) °. Template: room group / 15

The structure is that of clinopyroxene. Silicon (Si 4+ ) and aluminum (Al 3+ ) occupy the tetrahedral 4 oxygen ions surrounded T position, calcium (Ca 2+ ) is the octahedrally by 6 oxygens surrounded M2-position and the coordinated also octahedral M1-position is with Titanium (Ti 3+ ) occupied.

Education and Locations

So far, gross manite has only been found in calcium-aluminum-rich inclusions (CAIs) of some chondritic meteorites. Grossmanite is either a primary condensation product from the presolar mist or crystallizes from melts of melted and rapidly cooled CAIs.

The type locality is the Allende meteorite , a carbonaceous chondrite that fell on February 8, 1969 in the area around Pueblito de Allende near Parral in the state of Chihuahua in Mexico . Grossmanite was discovered here in CAIs, where it occurs together with spinel and perovskite or spinel, perovskite and grossite as an inclusion in gehlenite .

In a flaky Type-A CAI also from the Allende meteorite, a pyroxene rich in gross manite was found together with melilite, spinel and hibonite .

In the chondrites of the Rumuruti type (R-Chondrite) Dhofar1223 and NWA 1476, titanium-rich facades were found in some CAIs - but the oxidation level of the titanium was not determined.

Grossmanite with up to 20 wt. TiO 2 was found in the Ivuna CI1 chondrite . It occurs in the core of a CAI together with gehlenite, spinel and small amounts of anorthite and hibonite.

Grossmanit-rich Davisit and Kushiroit was also in a CAI of CV Chondrits RBT 04143 from Roberts Massif in Queen Maud Land , East Antarctica found (Antarctica). Titanium, aluminum and scandium-rich pyroxenes occur isolated or together with spinel, perovskite or spinel and perovskite as inclusions in gehlenite.

Web links

Individual evidence

  1. ^ Grossmanit in: IMA Database of Mineral Properties
  2. ↑ a b c d e f g h i j Chi Ma and George R. Rossman: Grossmanite, CaTi3 + AlSiO6, a new pyroxene from the Allende meteorite . In: The American Mineralogist . tape 94 , 2009, p. 1491–1494 ( rruff.info [PDF; 580 kB ; accessed on December 31, 2018]).
  3. ^ Grossmanit at mindat.org
  4. ↑ a b c d e f g Eric Dowty AND Joan R. Clark: Crystal Structure Refinement and Optical Properties of a Ti3 + Fassaite from the Allende Meteorite . In: The American Mineralogist . tape 58 , 1973, p. 230–242 ( minsocam.org [PDF; 1.6 MB ; accessed on January 2, 2018]).
  5. ^ A b Chi Ma, John R. Beckett, and George R. Rossman: Grossmanite, Davisite, and Kushiroite: Three Newly-approved Diopside-Group Clinopyroxenes in CAIs . In: Lunar and Planetary Science Conference . tape 41 , 2010 ( usra.edu [PDF; 996 kB ; accessed on December 17, 2018]).
  6. ^ Richard O. Sack, Mark S. Ghiorso: Thermodynamics of multicomponent pyroxenes: III. Calibration of Fe2 + (Mg) -1, TiAl2 (MgSi2) -1, TiFe3 + 2 (MgSi2) -1, AlFe3 + (MgSi) -1, NaAI (CaMg) -1, Al2 (MgSi) -1 and Ca (Mg) -1 exchange reactions between pyroxenes and silicate melts . In: Contributions to Mineralogy Petrology . tape 118 , 1994, pp. 271–296 ( springer.com [PDF; 253 kB ; accessed on January 6, 2018] preview).
  7. ↑ a b c Takashi Yoshizaki, Daisuke Nakashima, Tomoki Nakamura, Changkun Park, Naoya Sakamoto, Hatsumi Ishida, Shoichi Itoh: Nebular history of an ultrarefractory phase bearing CAI from a reduced type CV chondrite . In: Preprint . 2018 ( arxiv.org [PDF; 10.1 MB ; accessed on January 9, 2018]).
  8. ↑ Richard O. Sack, Mark S. Ghiorso: Ti3 + - and Ti4 + - RICH FASSAITES AT THE BIRTH OF THE SOLAR SYSTEM: THERMODYNAMICS AND APPLICATIONS . In: American Journal of Science . tape 317 , 2017, p. 807-845 , doi : 10.2475 / 07.2017.02 ( researchgate.net [PDF; 11.8 MB ; accessed on January 6, 2018]).
  9. ^ Lawrence Grossman: Vapor-condensed phase processes in the early solar system . In: Meteoritics & Planetary Science . tape 45 , 2010, p. 7–20 ( wiley.com [PDF; 2.0 MB ; accessed on December 23, 2018]).
  10. ↑ SB Simon, AM Davis and L. Grossman: Formation of orange hibonite, as inferred from some Allende inclusions . In: Meteoritics & Planetary Science . tape 36 , 2001, p. 331-350 ( wiley.com [PDF; 2.2 MB ; accessed on January 6, 2018]).
  11. ↑ Surya Snata Rout and Addi Bischoff: Ca, Al-rich inclusions in Rumuruti (R) chondrites . In: Meteoritics & Planetary Science . tape 43 , 2008, p. 1439–1464 ( uni-muenster.de [PDF; 12.1 MB ; accessed on January 9, 2018]).
  12. ↑ D. Frank, M. Zolensky, J. Martinez, T. Mikouchi, K. Ohsumi, K. Hagiya, W. Satake, L. Le, D. Ross, A. Peslier: A CAI IN THE IVUNA CI1 CHONDRITE. In: 42nd Lunar and Planetary Science Conference . 2011, p. 2785 ( nasa.gov [PDF; 259 kB ; accessed on January 6, 2018]).