Abstract:
We studied micropolycrystalline diamonds from modern and Neogene–Quaternary alluvial placers found in the main diamondiferous areas of Brazil (Minas Gerais, Bahia, and Mato Grosso). The polycrystalline inclusions were found as droplike crystals up to 50 × 70 μm in size (Figs. 1a, 1b), which are typical of zircon inclusions in mantle diamonds. In addition, such inclusions are found in diamond phase interstices as irregular aggregates (from 1 × 2 to 5 × 8 μ m in size) and in micropores as specific subspherical aggregates consisting of numerous crystals no more than 100–200 nm in size.
