Chromium(III) oxide, Cr 2 O 3, was used by the Chinese in the Qin Dynasty (秦朝, 259–210 ) to coat weapons, such as bronze crossbow bolts and steel swords found at the Terracotta Army (Fig. 5).The Terracotta Army (also called Terracotta Warriors and Horses) is a collection of terracotta sculptures depicting the armies of Qin Shi Huang, the first Emperor of China.