Ultramafic minerals from the Goat Hill serpentine barrens, Chester County, Pennsylvania, were examined using scanning electron and transmission electron microscopy in conjunction with energy dispersive spectroscopy, selected area electron diffraction, and electron energy loss spectroscopy. Magnesium-rich lizardite and clinochlore, antigorite, chrysotile, gahnite, Fe- and Fe-Cr spinels, and vernadite were the primary minerals with amorphous phases interspersed with the minerals. The Mn-oxide vernadite had a mixed Mn4+/Mn3+ oxidation state, with Mn4+ > Mn3+ and Ni > Fe.
Berti et al. (2026) studied this question.