Scientists understand how to better study iron, other minerals

Using Mössbauer spectroscopy, scientists investigate the iron ion status of pyroxenes, a major group of rock-forming silicate minerals. (Image by Keiji Shinoda, courtesy of Osaka Metropolitan University).

Researchers at Osaka Metropolitan University investigated the status of iron ions in monoclinic pyroxenes, an endeavour that is key for the future analysis of iron and other minerals’ flakes.

In a paper published in the Journal of Mineralogical and Petrological Sciences, the scientists explain that pyroxenes are a major group of rock-forming silicate minerals that generally contain calcium, magnesium, and iron. Given their abundance, elucidating the physical properties of pyroxenes is deemed vital in the study of rocks and minerals.

Monoclinic pyroxenes, specifically, are a type of calcium-rich pyroxenes.

Using Mössbauer spectroscopy on thin sections of single crystals, the Osaka team was able to show that in pyroxene crystals consisting of roughly 50% calcium, the tensor that determines the ratios of iron ions at the Mössbauer spectral peaks in the M1 sites—one of two types of cation positions in the pyroxene crystal structure—is independent of the iron content but dependent on the calcium content.

These results have clarified one of the physical properties of pyroxenes. At the same time, the findings may facilitate detailed future analysis of iron using Mössbauer spectroscopy on mineral flakes.

“We had expected that the tensor that determines the ratios at the Mössbauer spectral peaks would change if the iron solid solution component changed,” lead researcher Keiji Shinoda said in a media statement. “However, we were surprised to find that the tensor properties actually varied according to the content of calcium, rather than that of iron. This study’s findings provide practical data for researchers who are conducting a detailed analysis of iron by Mössbauer spectroscopy on mineral flakes.”

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