Various types of stone and glass jewellery have been found at neolithic sites across mainland Southeast Asia. They are evidence of technological advances in the way hard stones, probably sourced from riverbeds, were worked to produce status goods. Their wide distribution over long periods of time, also suggest the movement of people and goods in this region. Glass-working would have been a later development. The c-shaped or slit earring for example, is a form found in both stone and glass, associated with Dong Son culture, but also found at sites in Vietnam that date much earlier to the Phung Nguyen culture (2,500 - 1,400 BCE).