A mineral sample from the AuK2 diatreme site, Gloucester River, NSW, was studied by X-ray diffraction. It contains a gem association (ruby, sapphire, zircon, sapphirine) among minerals from xenolithic (almandine-rich garnet, diopside, spinel) and megacryst (phlogopitic mica, hastingsitic amphibole, rutile) suites and from quartzose components within Carboniferous sedimentary beds. The grain characteristics suggest a proximal source or sources. Fission track dating of zircons gave three separate ages, Palaeocene (62 Ma) for moderate uranium content zircons, Eocene (39 Ma) for low U zircons and Pliocene (4 Ma) for high U zircons. This implies either repeated eruptions among Gloucester River diatremes or incomplete thermal resetting of zircons. The AuK2 sample suggests diatremes play a role as gem sources in the Barrington field.