©Lin Yangchen


Microscope: ‘Special Forces’ Olympus BHSP

This website is one of the very few to present meteorite thin section micrographs in both transmitted and reflected light. Analyses are dependent on my progressive study of meteorite mineralogy and may not be error-free. Please contact me if you spot mistakes so I can correct them and make this a better reference for everyone. Also see my terrestrial petrography page and disco lighting videos..




Accession no. R010


Locality: Kerman, Iran
Sample date: 2 April 2016
Method: hand sample
Finder: Timur Valer'evich Kryachko and Khatami Majid, Iranian-Russian expedition




Macroscopic description

Gandom Beryan meteorite. Ordinary chondrite of primitive material from the early Solar System. Covered by dark brown fusion crust. Weathering grade (see Wlotzka 1993) W1 (light oxidation).


Petrographic analysis


Polished with 0.5 μm diamond paste on 2 mm glass slide with no coverslip
prepared by Timur Kryachko

Class L3 subtype 3.6 (low-iron unequilibrated mineral assemblage slightly metamorphosed). Shock stage S1 (no shock metamorphism). Disco lighting videos: low | high magnification


Going back 4,500,000,000 years to the time when the Solar System was a spinning disc of gas and dust.

 
 
Radial pyroxene (RP) chondrule formed by rapid cooling of molten ore, with a porphyritic rim resembling a mediæval stone wall and an opaque outer fine-grained rim of sticky nebular dust that accreted in an environment of turbulence and electrostatic forces and helped chondrules aggregate into larger bodies. Left, transmitted; right, reflected. Top, plane-polarized; bottom, cross-polarized. Bright white patch at upper left of reflected plane-polarized micrograph is metal, probably native iron.


Length slow or positive sign of elongation with 530 nm retardation plate.

 
 
Part of a large porphyritic olivine pyroxene (POP) chondrule with occasional glass and opaque grains. Left, transmitted; right, reflected. Top, plane-polarized; bottom, cross-polarized.


A pair of poikilitic pyroxene chondrules with contrasting olivine grain sizes, different twinning and extinction morphologies, and oxidation stains. See video.

 
 
Olivine bundled with fibrous material. Left, transmitted; right, reflected. Top, plane-polarized; bottom, cross-polarized. Darker grey phases in reflected plane-polarized light are usually indicative of feldspar compared with the lighter grey silicates.

 
 
Cratered cryptocrystalline chrondule with layered bleached rim (evidence of aqueous alteration of parent body) and thin glassy outer rim. Left, transmitted; right, reflected. Top, plane-polarized; bottom, cross-polarized.

 
Polysomatic barred olivine.

 
Conoscopic fourier transform optic axis interference figures of a biaxial positive mineral. Numerical aperture 0.80.


An opaque grain in reflected plane-polarized (top) and cross-polarized (bottom) light, possibly composed of kamacite (light bluish grey and isotropic), taenite (cream) and troilite (FeS iron sulphide, tan). Bluish grey phases could also be oxides or chromite. Cross-polarization reveals internal reflections and oxidation weathering that has stained the surrounding silicates.





Meteorite databases & atlases

Marmet meteorites
Derochette meteorite thin sections





References

Barbre, K. S. R., Davis, R. E. & Regberg, A. B. 2020. Fungal exposure to meteorite thin sections: developing an experimental to observe biogeochemical changes. 51st Lunar and Planetary Science Conference.

Barosch, J., Hezel, D. C., Sawatzki, L., Halbauer, L. & Marrocchi, Y. 2020. Sectioning effects of porphyritic chondrules: implications for the PP/POP/PO classification and correcting modal abundances of mineralogically zoned chondrules. Meteoritics & Planetary Science 55(5):993–999.

Carballido, A., Xiang, C., Hanna, R. D., Matthews, L. S. & Hyde, T. W. 2021. Early accretion of chondrule dust rims. 52nd Lunar and Planetary Science Conference.

Connolly, H. C. Jr. & Hewins, R. H. 1991. The experimental production of chondrule rims: constraints on chondrule rim origins. LPSC XXII.

Grossman, J. N. 1998. Radial pyroxene and cryptocrystalline chondrules as indicators of aqueous alteration and thermal metamorphism in ordinary chondrites. Lunar and Planetary Science XXIX.

Grossman, J. N., Alexander, C. M. O'D., Wang, J. & Brearley, A. J. 2000. Bleached chondrules: evidence for widespread aqueous processes on the parent asteroids of ordinary chondrites. Meteoritics & Planetary Science 35:467–486.

Hewins, R. H., Connolly, H. C. Jr., Lofgren, G. E. & Libourel, G. 2005. Experimental constraints on chrondrule formation. In Chondrites and the Protoplanetary Disk, ASP Conference Series Vol. 341 eds. Krot, A. N., Scott, E. R. D. & Reipurth, B. pp. 286–316.

Kostynick, R. P. 2019. Bleached chondrules and the possible influence of aqueous alteration. Portland State University honors thesis.

Merrill, G. P. 1920. On chondrules and chondritic structure in meteorites. Proceedings of the National Academy of Sciences 6(8):449–472.

Musolino, A. & Folco, L. Atlas of Meteorites in Thin Section. Dipartimento di Scienze della Terra, Università di Pisa.

van Kooten, E. M. M. E., Moynier, F. & Agranier, A. 2019. A unifying model for the accretion of chondrules and matrix. Proceedings of the National Academy of Sciences of the United States of America 116(38):18860–18866.

Varela, M. E. 2016. Glasses in chondrules: understanding the role of liquids during chondrule formation processes. 47th Lunar and Planetary Science Conference.

Voort, G. F. V. 1992. A note on metallographic techniques for iron meteorites. Materials Characterization 29:223–241.

Wlotzka, F. 1993. A weathering scale for the ordinary chondrites. Meteoritics 28(3):460.

Xiang, C., Matthews, L. S., Carballido, A. & Hyde, T. W. 2019. Modeling the growth of chondrule dust rims under various plasma conditions. 50th Lunar and Planetary Science Conference.
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