Zitan wood
Zitan wood is considered in China to be the most precious type of wood, first referenced in Chinese history in the third century. It was the hardest and heaviest of 6 hardwoods used to create furniture, the other 5 being Huanghuali, Jichimu, Tiuelimu, Wumu and Hongmu. It can be jet black, dark purple, or purple-red, and has a very close grain. The unique characteristics of zitan wood gave it the privilege of being reserved solely for Imperial use by the time of the reign of the Qianlong Emperor.