James Watt opinon 11/6/1987: earlier than Western Zhou; late Neolithic/early Shang.
Wen Guang opinon 12/5/00: the stone was from xi-bei and contemporary with Qijia/Longshan 2500-2000 BC. It was no longer available after W. Zhou.
Knife-shaped and axe-shaped blades made from stone were probably working tools in Neolithic societies. The Chinese also made blades from jade. This beautiful mineral is hard but brittle, so the blades are unlikely to have been put to practical use. Instead they would have been held by chieftains as symbols of authority. Large quantities of jade blades have been excavated in different regions in China, indicating their widespread use over a span of more than 3,000 years.