A Neolithic Lapidary Problem
Between 3300 and 2300 BCE, a sophisticated culture flourished in the Yangtze River Delta. Known today as the Liangzhu, these people left behind no writing system, but they did leave thousands of finely worked jade objects that show a mastery of materials science. The primary material was nephrite, a mineral with a hardness of 6.0 to 6.5 on the Mohs scale. This presented a significant technological challenge, as the Liangzhu possessed no metal tools hard enough to carve it.
Their solution was abrasion. Scientific analysis shows the Liangzhu used harder minerals, likely quartz sand (Mohs hardness 7), and tools made of stone, wood, or bamboo to slowly grind the nephrite into shape. The process involved sawing, drilling, and polishing, all driven by manual labor. Microscopic examination of the artifacts reveals the techniques used, such as drilling holes from both sides of an object to meet in the middle. The final polish had a glossy, almost liquid luster that modern techniques, even with diamond abrasives, find difficult to replicate.
Ritual Forms in Stone
Two object types dominate Liangzhu burial sites: the bi and the cong. The bi is a flat, circular disc with a central hole. Their purpose is unknown, but they were often laid on the bodies of the dead in high-status tombs. The cong is a more complex shape: a square-sectioned tube with a circular hole bored through its length. These objects range from small, bracelet-like pieces to enormous examples. The largest, dubbed the "King of Cong," stands 8.9 cm high and weighs 6.5 kilograms.
The corners of the cong are decorated with face patterns, often interpreted as human-animal hybrids or deities. These designs are rendered in fine, shallow relief. Some carved lines are barely visible to the naked eye. The function of these objects is unknown, though a common hypothesis suggests the square cong represented the Earth while the circular bi represented the heavens. In one elite tomb at the Fanshan cemetery, archaeologists found 25 bi and 33 cong buried with a single individual.
The Archaeological Ruins of Liangzhu City, a UNESCO World Heritage site since 2019, reveals a complex society with urban planning, large-scale water management systems, and a clear social hierarchy expressed through these jade objects found in burials.