Cinnabar
From Shadow of the Throne Wiki
Appearance: Often similar to Quartz in shape, but with a brilliant red or scarlet coloration.
Description: Cinnabar is a gemstone commonly found where flows of Earth, Fire, and Water Essence intertwine, such as the volcanic peaks of the Southern mountains or the hot springs of the Blessed Isle. Cinnabar is rarely used for jewelry, instead being processed to provide a vibrant red pigment (particularly favoured by the Scarlet Empress and Her Realm, used in clothing and art including Carved Lacquer) or Quicksilver.