In one of the diamond crystals from the Juina area, Brazil, an association:
wüstite+periclase was identified. Earlier iron-rich periclase and
magnesiowüstite were known from other areas: in a diamond from
the Monastery pipe, South Africa, a grain with mg=0.12 was found
(Moore et al., 1986), and in a diamond from the Guaniamo area, Venezuela,
almost pure wüstite with mg=0.002 was found