Troilite nodule
A troilite nodule is a rounded or elongated lump of iron sulfide in an iron meteorite.
A troilite nodule is a bronze-coloured lump of iron sulfide, typically millimetres to several centimetres across, embedded in the metal of an iron meteorite. On a polished and etched slice it stands out as a golden or brownish blob, often surrounded by a rim of graphite, schreibersite or chromite.
The nodules formed because sulfur did not dissolve easily into solid metal as an asteroid core froze. Droplets of iron sulfide melt were trapped and later solidified. Some nodules contain plates of daubréelite or tiny grains of other minerals that separated out as they cooled.
Troilite nodules are attractive features for collectors but can be troublesome: they are softer and more brittle than the metal and may crack or weather faster. Scientifically, they contain lead with a very low uranium content, which is why troilite from the Canyon Diablo iron was used to define the primordial lead composition of the Solar System.
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