Niu Qiong, the sixth-generation inheritor of Yigong Tibetan knife, forges two different metals together to make a knife in Yigong Township of Nyingchi, southwest China's Tibet Autonomous Region, May 30, 2019. Yigong knife is an intangible cultural heritage of Tibet Autonomous Region. It takes about one month to make such a knife. (Xinhua/Jigme Dorje)

Niu Qiong, the sixth-generation inheritor of Yigong Tibetan knife, makes a knife in Yigong Township of Nyingchi, southwest China's Tibet Autonomous Region, May 30, 2019. Yigong knife is an intangible cultural heritage of Tibet Autonomous Region. It takes about one month to make such a knife. (Xinhua/Jigme Dorje)

Niu Qiong, the sixth-generation inheritor of Yigong Tibetan knife, shows a knife he made in Yigong Township of Nyingchi, southwest China's Tibet Autonomous Region, May 30, 2019. Yigong knife is an intangible cultural heritage of Tibet Autonomous Region. It takes about one month to make such a knife. (Xinhua/Jigme Dorje)

Niu Qiong, the sixth-generation inheritor of Yigong Tibetan knife, makes a knife in Yigong Township of Nyingchi, southwest China's Tibet Autonomous Region, May 30, 2019. Yigong knife is an intangible cultural heritage of Tibet Autonomous Region. It takes about one month to make such a knife. (Xinhua/Jigme Dorje)

Niu Qiong, the sixth-generation inheritor of Yigong Tibetan knife, checks out the refined iron ore in Yigong Township of Nyingchi, southwest China's Tibet Autonomous Region, May 30, 2019. Yigong knife is an intangible cultural heritage of Tibet Autonomous Region. It takes about one month to make such a knife. (Xinhua/Jigme Dorje)