X-ray Laue Microdiffraction and Raman Spectroscopic Investigation of Natural Silicon and Moissanite

Abstract

Moissanite, SiC, is an uncommon accessory mineral that forms under low oxygen fugacity. Here, we analyze natural SiC from a Miocene tuff-sandstone using synchrotron Laue microdiffraction and Raman spectroscopy, in order to better understand the SiC phases and formation physics. The studied crystals of SiC consist of 4H- and 6H-SiC domains, formed from either, continuous growth or, in one case, intergrown, together with native Si. The native Si is polycrystalline, with a large crystal size relative to the analytical beam dimensions (>1–2 μm). We find that the intergrown region shows low distortion or dislocation density in SiC, but these features are comparatively high in Si. The distortion/deformation observed in Si may have been caused by a mismatch in the coefficients of thermal expansion of the two materials. Raman spectroscopic measurements are discussed in combination with our Laue microdiffraction results. Our results suggest that these SiC grains likely grew from an igneous melt.

Evidence of the anthropogenic origin of the ‘Carmel sapphire’ with enigmatic super-reduced minerals

“…2O7 (Ma et al, 2021); ziroite (IMA2022-013) ZrO2 ; sassite (IMA2022-014) Ti 3+ 2Ti 4+ O5 ; mizraite-(Ce) (IMA2022-027) Ce(Al11Mg)O19 ; toledoite (IMA2022-036) TiFeSi ; and yeite (IMA2022-079) TiSi . Grain aggregates of CS (and also hibonite and moissanite) from Carmel have been the objects of numerous scientific publications (Griffin et al, 2016(Griffin et al, , 2018(Griffin et al, -2022Xiong et al, 2017; https://doi.org/10.1180/mgm.2023.25 Published online by Cambridge University Press Dobrzhinetskaya et al, 2018;Cámara et al, 2019;Bindi et al, 2019Bindi et al, , 2020Huang et al, 2020;Stan et al, 2020;Oliveira et al, 2021;Lu et al, 2022), in which the authors present the highly controversial hypothesis that the corundum rock with SR minerals formed at the crust-mantle boundary as a result of CH4+H2 fluid flowing through the magmatic melt.…”

“…This corundum with inclusions of super-reduced minerals obtained the trademark ‘Carmel sapphire’ and has been the host of 10 new mineral species discovered in the last five years and approved by the Commission on New Minerals, Nomenclature and Classification (CNMNC) of the International Mineralogical Association (IMA): carmeltazite (IMA2018-103) ZrAl 2 Ti 4 O 11 (Griffin et al , 2018); kishonite (IMA2020-023) VH 2 (Bindi et al , 2020); oreillyite (IMA 2020-030a) Cr 2 N (Bindi et al , 2020); griffinite (IMA 2021-110) Al 2 TiO 5 (Ma et al , 2022a); magnéliite (IMA2021-111) Ti 3+ 2 Ti 4+ 2 O 7 (Ma et al , 2022b); ziroite (IMA2022-013) ZrO 2 (Ma et al , 2022c); sassite (IMA2022-014) Ti 3+ 2 Ti 4+ O 5 (Ma et al , 2022d); mizraite-(Ce) (IMA2022-027) Ce(Al 11 Mg)O 19 (Ma et al , 2022e); toledoite (IMA2022-036) TiFeSi (Ma et al , 2022f); and yeite (IMA2022-079) TiSi (Ma et al , 2023). Grain aggregates of Carmel sapphire (and also hibonite and moissanite) from Carmel have been the objects of numerous scientific publications (Griffin et al , 2016a,b, 2018, 2019a,b, 2020a,b, 2021a,b, 2022; Xiong et al , 2017; Dobrzhinetskaya et al , 2018; Cámara et al , 2019; Bindi et al , 2019, 2020; Huang et al , 2020; Stan et al , 2020; Oliveira et al , 2021; Lu et al , 2022), in which the authors present the highly controversial hypothesis that the corundum rock with super-reduced minerals formed at the crust–mantle boundary as a result of CH 4 +H 2 fluid flowing through the magmatic melt.…”