Concept
Version 6
Created by Boundless
Jade in Neolithic China
Neolithic cong, 3rd millennium BCE
The cong is a Chinese jade vessel, square on the outside but circular on the inside.
Source
Boundless vets and curates high-quality, openly licensed content from around the Internet. This particular resource used the following sources:
"800px-Chinese_-_Cong_-_Walters_42340_-_Profile.jpg."
https://en.wikipedia.org/wiki/Chinese_jade#/media/File:Chinese_-_Cong_-_Walters_42340_-_Profile.jpg
Wikipedia
Public domain.