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Yuyuliang (Hematitum), grows in the pools and marshes of the East Sea as well as on mountain islands, or within the pools. Currently, it is only found in Zezhou and Luzhou. Old descriptions state that its shape resembles goose or duck eggs, with an outer shell consisting of overlapping layers, containing a yellow interior that, when ground into fine powder, resembles Puhuang (Cattail Pollen). The illustrations in current texts depict it entirely as mountain stone shapes, lacking any egg-like form, which differs slightly from old descriptions. It can be harvested at any time.

The *Shennong Bencao Jing* also mentions Taiyi Yuliang (Taiyi Hematitum). According to Tao Hongjing's *Dengzhen Yinjue*, the prescription for Changsheng Sizhen Wan states: "Taiyi Yuyuliang stabilizes the Six Fu-organs and anchors the Five Zang-organs." The annotation notes: "According to Bencao, there are two types: Taiyi Yuliang and Yuyuliang; their therapeutic properties are essentially the same. However, in contemporary times, only Yuyuliang is known, and Taiyi is no longer recognized. Consequently, this prescription combines both names, making it impossible to distinguish which is the authentic material." Later texts simply state: "For Yuyuliang, it should be used as contained in the box." Yuyuliang is mostly produced along the banks of mountains in Dongyang, and Mount Mao has abundant supplies. The high-quality specimens resemble Niuhuang (Calculus Bovis), with layered, armor-like textures. The finest parts are purple, fine as flour, and do not feel gritty when chewed. Although usable, it must be finely ground and washed with water to extract the juice, ensuring no sand or soil remains. Su Gong also stated: "Taiyi Yuliang and Yuyuliang are originally the same substance, distinguished by refinement. Hence, one name is Taiyi Yuyuliang. Its shell resembles porcelain. Initially uncoagulated inside the shell, it is yellow liquid; after long coagulation, it exhibits various colors—green, white, red, or yellow. Over many years, it gradually turns purple. Those ranging from red to purple are called Taiyi, while all other colors are collectively referred to as Yuliang." Contemporary physicians use Yuliang without such detailed differentiation. Zhang Zhongjing treated persistent dysentery due to Cold Damage, accompanied by epigastric fullness and hardness, where the pathology was located in the Lower Jiao, using Chishizhi Yuyuliang Tang (Red Halloysite and Hematitum Decoction). The formula consists of Chishizhi (Halloysitum Rubrum) and Yuyuliang (Hematitum), each 1 jin, crushed together, boiled in 6 sheng of water until 2 sheng remain, filtered, and divided into two doses.

Furthermore, according to Zhang Hua's *Bowuzhi*: "On Fuhai Island, there is a grass named [missing character] cao. Its fruit is edible, resembling Da Mai (Hordei Fructus Germinatus). It ripens from the seventh month, and people harvest it until winter ends. It is called Ziran Gu (Natural Grain) or also Yuyuliang." In modern pharmacopeia, Yuyuliang is said to have originated from Yu the Great throwing his leftover food into the river during flood control, which then transformed into medicine. Thus, the [missing character] grass and this mineral are different substances sharing the same name. Does the legend of it transforming from food thrown into the river imply it is the same species as those growing in sea pools and marshes?