https://phys.org/news/2018-06-exploring-dusty-prehistory-solar.html

Now, a multi-institutional collaborative of researchers has published a study drawing multiple inferences about the nature of presolar dust based on these observations, as well as data gathered from the Cosmic Dust Analyzer (CDA) aboard the Cassini Saturn orbiter during its two-decade mission; in their paper, published in the Proceedings of the National Academy of Sciences, they present a detailed description of presolar dust aggregation that fits the new data.

They start by proposing that GEMS formed within the interstellar medium via grain shattering, amorphization and erosion from supernovae shocks, and experienced subsequent periods of aggregation. "With repeated cycling in and out of cold molecular clouds, mantled dust and any aggregates were repeatedly and progressively partially destroyed and reformed. Cassini mission data suggest the presence of iron metal in contemporary interstellar dust," the researchers write. They believe irradiation within the interstellar medium provided enough energy to incorporate small amounts of metal atoms within the amorphous silicates comprising the dust.