Spectroscopic research on ultrahigh pressure (UHP) macrodiamond at Copeton and Bingara NSW, Eastern Australia

► 98% of 2 million alluvial macrodiamonds from Eastern Australia come from 0.6% of area (Copeton/Bingara-C/B). ► Raman test shows C/B diamond not cratonic. ► Raman of C/B diamond inclusions indicate ultrahigh pressure formation during subduction. ► IR spectra of C/B diamond shows N abundance and aggregation change significantly but coherently across C/B district. ► Requires multiple local basaltic sources (Tertiary to Jurassic) for C/B diamonds.