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(Recorded in the Lower Grade of *Bencao Jing Jizhu* / Supplement to the Materia Medica)

**[Names]** Cangshi (Cyan Alum Stone), Teshengshi (Specially Generated Stone) (*Bencao Jing Jizhu*), Shudu (Rat Poison).
Su Gong stated: Teshengshi is also known as Cangshi. Stones from Liangzhou are sometimes blue-green; people in Hanzhong use them to poison rats, but they are not used in medical prescriptions.
Su Song stated: Teshengshi and ordinary stones are essentially the same substance, distinguished only by whether they are "Tesheng" (specially generated/standalone). "Tesheng" refers to stones that do not adhere to other rocks. They are rarely used nowadays.
Li Shizhen stated: There are two types of this stone: cyan and white. The cyan variety is mostly Teshengshi. Thus, stating it is also named Cangshi implies that the Cangshi recorded in *Bencao Jing Jizhu* is a duplicate entry. Their therapeutic effects are identical, so they are now combined into one category.

**[Collection and Explanation]** *Bencao Jing Jizhu* states: Teshengshi, also called Cangshi, originates from the Western Regions, with no fixed time for collection. It further states: Cangshi originates from the Western Regions, with no fixed time for collection.
Tao Hongjing stated: Old theories suggest that stones found in stork nests are of superior quality. Since storks frequently enter cold water, these stones were taken to wrap eggs to keep them warm. Such stones are now unavailable. Those from Hanzhou are preferred if they have a purple-red exterior, an interior white like frost, a central depression resembling a mortar, and a shape like teeth. Additionally, those from Fangling County, Xincheng Commandery, Jingzhou, which are pale white, are considered good. Before use, they should be wrapped in yellow earth and fired for one day, or heated in an axe hole, to prepare pills such as Yuhu Wan. The *Xianjing* (Classic of Immortals) does not mention Teshengshi, referring only to white alum stones.
Su Gong stated: Tao's description of the tooth-and-mortar shape is correct. Currently, they are produced in Liangzhou, including in the streams at Beimaodao Shu. The lumps are smaller than white alum, but their crystalline grains are several times larger, about the size of a small bean, whereas white alum grains are fine like millet seeds. In places where Fangling, Hanchuan, Zhongzhou, and Jingzhou overlap with white alum sources, there are blue-green varieties, which are this type.
Su Song stated: *Bowuzhi* (Insects and Animals) mentions that storks place these stones in their nests to assist in warming eggs during incubation; only when alchemists obtain this stone is it considered genuine.
Tao Hongjing annotated this as Teshengshi, clearly indicating that the two stones are the same substance. However, upon repeatedly checking stork nests, this stone was not found. Moreover, how could this stone be ubiquitous? If storks take this stone because they enter cold water, then cormorants, which also feed in water, should naturally undergo biochemical proliferation. This is merely the talk of laymen who have not investigated the reality and principles thoroughly.
Li Shizhen stated: There are several varieties of alum stones: Baihua Shi (White Alum), Canghua Shi (Cyan Alum), Zihua Shi (Purple Alum), Hongpi Shi (Red Skin Alum), Taohua Shi (Peach Blossom Alum), Jin Xing Shi (Gold Star Alum), Yin Xing Shi (Silver Star Alum), and Teshengshi are all the same substance, named solely based on color and shape.
Their nature is hot and toxic; they can all be used to poison rats and control mercury. Only the cyan and white varieties are used medicinally. Wherever alum stones grow in mountains, grass and trees do not grow, and frost and snow do not accumulate; where they grow in water, the water does not freeze, or hot springs may appear, revealing their hot nature. *Gengxin Yuce* states: Alum is a Yang stone, growing in valleys. Those washed out of water resemble Mingfan (Alum), and those with transverse textures in the center are superior. After fire-processing to subdue its fire nature, it can control sand-mercury. Its appearance is quite similar to Calcite, but the genuine article does not freeze when thrown into water. Those found in gold mines are called Woxue Shi (Snow-Holding Stone).

**[Flavor and Properties]** Sweet, Warm, Toxic.
Xu Zhicai stated: Fire-refined is best; it fears water.

**[Indications]** Brightens the eyes and benefits the ears; treats extreme cold within the abdomen; breaks up hard accumulations and rat ulcers; kills hundred insects and fierce beasts. Long-term consumption prolongs life (*Bencao Jing Jizhu*). Cangshi: Treats alternating chills and fever, directs Qi downward, and treats erosive sores; kills birds and beasts (*Bencao Jing Jizhu*).

**[Elucidation]** Li Shizhen stated: *Bencao Jing Jizhu* says: Long-term consumption of alum causes muscle spasms, while long-term consumption of Teshengshi prolongs life. Alchemical texts also state: Alum transforms into water and can fix mercury; when refined and added to longevity medicines... These are all erroneous claims by Daoist alchemists, similar to the logic of consuming realgar and mercury for immortality. Are those who die without regret truly wise?