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[Mayaxiao (Horse-Tooth Nitre)]
Taste: Sweet. Nature: Very Cold. Toxicity: Non-toxic. It can eliminate accumulated heat and latent qi in the five zang organs. When sifted into fine powder for eye application or added to eye medicines, it is very effective in removing redness, swelling, nebula, astringency, tearing, and pain. (Newly supplemented content, found in *Yaoxing Lun* and recorded by Ri Huazi.)
The text from *Tu Jing* is detailed under the entry for Puxiao (Mirabilite).

Empirical Formula: For treating epigastric fullness and obstruction caused by overeating and indigestion. Take 1 liang of Mayaxiao, crush it; take half sheng of aged Evodia fruit (Wuzhuyu), decoct to extract a concentrated juice, pour it into the nitre, and drink while hot. If there is no bowel movement after a long time, administer another dose, and recovery will be immediate. This formula proved effective when Dou Qun was in Changzhou.
Another Formula: Bai Long San (White Dragon Powder) for reducing nebula and improving vision. Select bright and clean Mayaxiao, wrap it tightly in thick paper, and place it against the skin inside clothing. Maintain this for 120 days, then take it out and grind it into powder. Add a small amount of Borneol (Longnao) and grind finely together. Regardless of how long the disease has persisted, as long as the pupil is not ruptured or scattered, any nebula formed inside the eye, gradual dimness, and blurred distance vision can be cured. Apply approximately the size of a rice grain of the powder into the eye each time.
*Jian Yao Ji Zhong Fang*: For treating infant thrush. Finely grind Mayaxiao and sprinkle it on the tongue, three to five times daily.
Formula by Yao Hezhong: For treating infant double tongue. Apply Mayaxiao to the sublingual area, three times daily.
*Tai Qing Fu Lian Ling Sha Fa*: Mayaxiao is the essence of extreme Yin; it can restrain Yang essence and dissipate the qi of fire stones.
*Dan Fang Jing Yuan*: Used for nurturing cinnabar and processing sulfur compounds.

[Shengxiao (Raw Nitre)]
Taste: Bitter. Nature: Very Cold. Toxicity: Non-toxic. It primarily treats epilepsy due to wind-heat, pediatric convulsions and spasms due to fright, wind-dizziness and headache, lung congestion, deafness, mouth ulcers, throat bi with swallowing difficulty, swelling and pain of the jaw, red and hot painful eyes, excessive discharge and tearing. It grows on the rocks of West Mountain in Maozhou. The lumps vary in size, and the color is greenish-white. It can be harvested at any time. (It is incompatible with Maijujiang. Added note.)
The text from *Tu Jing* is appended under the entry for Puxiao.

[Hua Shi (Talcum)]
Taste: Sweet. Nature: Cold, Very Cold. Toxicity: Non-toxic. It treats fever, diarrhea, lactation difficulties in women, strangury and urinary retention, promotes urination, sweeps away accumulated cold and heat in the stomach, benefits essence and qi, unblocks the nine orifices and six fu organs' fluids, removes stagnation and accumulation, stops thirst, and makes the body feel light. Long-term use leads to a light body, resistance to hunger, and longevity. Also known as Yeshi, Gongshi, Tuoshi, and Fanshi. It grows in the valleys of Zheyang and on the north slope of Mount Tai, or in Baishan north of Yexian, or in Juan Mountain. It can be harvested at any time. (Pyrrosiae Folium is its assistant herb; it is incompatible with Tsengqing.)

Tao Hongjing stated: Hua Shi is pure white; *Xian Jing* uses it as mud. There is also Leng Shi, which is pale greenish-yellow, and both have cold and purgative properties; they can also be used to iron oil stains on clothes. Currently, it is produced in Xiangzhou, Shian Commandery, and other places. When first extracted, it is soft like mud, but gradually hardens over time. People often use it to make lighting vessels for tombs and for cooling purposes, but it is not formally used in prescriptions. Zheyang County previously belonged to Nanyang Commandery and was established during the reign of Emperor Ai of Han; thus, the commanderies and counties noted in *Ben Jing* must refer to those of the Later Han dynasty. Yexian belongs to Donglai Commandery, Qingzhou; Juan County belongs to Rongyang, Sizhou. *Tang Ben Zhu* states: This stone is available everywhere. Those from Shian in Lingnan are white like congealed fat and extremely smooth. Those from Yexian have coarse texture, are greenish-white with black spots, and can only be used for vessels, not for medicine. There is also a large production in the South Valley of Shentong Temple, South Mountain of Qizhou; the color is greenish-white but inferior, though its smoothness still surpasses that from Yexian.臣 Yuxi et al. carefully followed *Yaoxing Lun*, stating: Hua Shi is a minister herb. Also known as Xileng. It treats the five stranguries and difficult labor. Taking its powder, or making a paste with powder, Danshen, honey, and pig fat, and taking it orally with wine in the morning before eating when the delivery month arrives, helps. Double the dose at childbirth to facilitate easy delivery. It relieves vexation, heart heat, and restlessness, primarily treating stone strangury. Chen Cangqi stated: According to the two types from Shian and Yexian, their shapes and qualities differ, and their uses are distinct. Tao said: I do not know if it exists in the North now. During Tao's time, the North was blocked off, so ignorance is not surprising. Su Gong grouped them as one substance, which is deeply astonishing. The Shian variety is soft, smooth, and white, which is Hua Shi. The Donglai variety is hard, astringent, and green, which is a vessel-making stone. *Nan Yue Zhi* states: Cheng County produces Tan Shi, and Tan Shi is Hua Shi. Locals use it to fire vessels for cooking fish. Ri Huazi stated: Hua Shi treats breast abscesses and promotes fluid secretion.

*Tu Jing* states: Hua Shi grows in the valleys of Zheyang, the north slope of Mount Tai, Baishan north of Yexian, or Juan Mountain. Currently, it is found in Daozhou, Yongzhou, Laizhou, and Haozhou. There are two types. Those from Daozhou and Yongzhou are white and smooth like congealed fat. *Nan Yue Zhi* states: Cheng County produces Tan Shi, and Tan Shi is Hua Shi. Locals use it to fire vessels for cooking fish, referring to this. Those from Laizhou and Haozhou have coarse texture, are green with black and white spots, and are also called Ban Shi. Both types can be used for vessels and are of high quality. Initially soft and rotten like mud, they gradually harden. Locals carve them while soft in caves, requiring little effort; otherwise, they are hard...
*Lei Gong Pao Zhi Fang* states: Hua Shi comes in five colors; one should use the white type resembling Calcitum (Fangjie Shi). The green type is cold in nature and toxic, and is not used in medicine. It further states: Genuine Hua Shi resembles ice, is white-greenish, and has white greasy patterns when drawn on stone. With this description, it aligns with those coming from the South, leaving no doubt in usage. However, although Lei Xiao is named as a Sui dynasty person, his book mentions post-Tang medicinal names, suggesting later additions or modifications. Some say: Yizhou produces a superior type of Hua Shi, consistent with the north slope of Mount Tai mentioned in *Ben Jing*. However, locals do not harvest it for medicine, so physicians rarely know to use it. The green Hua Shi supplied by physicians in Haozhou is described as slightly cold and non-toxic, treating stagnant heart qi. This is largely similar to *Ben Jing* with minor differences. *Wu Lu Di Li Zhi* and *Tai Kang Di Ji* state: Bushan County in Yulin Prefecture has many vipers whose venom kills; Leng Shi can antidote it. The stone is reddish-black, bitter in taste, and when ground and applied to wounds, biting teeth brings immediate relief. Also known as Qichi Shi. Now, people often use Leng Shi powder to treat prickly heat, saying it is Hua Shi, differing only in bitter vs. sweet taste. Ancient formulas for promoting urination and treating strangury often used Hua Shi alone. Combined with Pyrrosiae Folium, ground to powder, and taken with water in the measure of Dao Gui, it acts faster. It also treats stone strangury with vexation and stuffiness: take 12 fen of Hua Shi, grind to powder, divide into two doses, mix with water, stir until dissolved, and take all at once. Once vexation and heat settle, stop subsequent doses. If not resolved, completing the dose ensures cure.

Lei Gong said: There are various types; do not mistake them. There are White Hua Shi, Green Hua Shi, Black Hua Shi, Cold Hua Shi, and Yellow Hua Shi. Among them, White Hua Shi is Fangjie Shi, white in color, with white greasy patterns on the stone, which is usable. Green Hua Shi is cold and toxic, not for medicinal use. Black Hua Shi is dark-colored, with blue-white greasy patterns on the stone, suitable for use. Yellow Hua Shi is gold-colored and round; those with blue-black patterns on the stone should not be used as they are poisonous. Cold Hua Shi is cyan-green, with white greasy patterns on the stone, also not to be used. Genuine Hua Shi resembles ice, is white-greenish, and has white greasy patterns when drawn on stone. To process: scrape with a knife, grind to powder, boil with Cortex Moutan for one shichen (two hours), remove, discard Moutan, take the Hua Shi, wash with flowing water from the east, and dry in the sun before use. *Sheng Hui Fang*: For treating "milk stone" activation causing restless heat, vexation, and unquenchable thirst. Grind 0.5 liang of Hua Shi to fine powder, add one zhong of water, squeeze to obtain a white liquid-like juice, and take in one dose. If not cured, take again. Another formula: For treating bladder torsion caused by holding urine too long. Take Hua Shi powder, mix with scallion soup, and swallow with two qianbi. Another formula: For upper diaphragm vexation, heat, and excessive thirst, unblocking the nine orifices. Crush 2 liang of Hua Shi, decoct in three zhong of water to reduce to two zhong, remove dregs, add two he of japonica rice, cook into porridge, and eat warm for efficacy. *Wai Tai Mi Yao*: For pregnancy with inability to urinate, mix Hua Shi powder with water to form mud, apply to two cun below the navel. *Guang Li Fang*: For qi congestion, guan-ge obstruction, strangury with結 (knotting), and lower abdominal discomfort/pain. Grind 8 fen of Hua Shi to flour consistency, mix with five he of water, stir well, and take in one dose. *Yang Shi Chan Ru*: For urinary obstruction. Take one sheng of Hua Shi powder, mix with juice of Plantago seed (Cheqian), apply around the navel in a four-cun square area; change when hot; using water in winter is also acceptable. *Dan Fang Jing Yuan*: Hua Shi can be used to prepare external containers for Realgar and Orpiment. *Zhou Li*: "Nourish orifices with slipperiness." Commentary states: Hua Shi. All things that promote flow and movement resemble orifices.

*Yan Yi* states: Hua Shi is now called Hua Shi (Drawing Stone) because it is soft and slippery for writing/drawing; it is frequently used by patients with strangury. If sudden vomiting occurs preventing food intake, take two qianbi of raw fine powder with warm water; simultaneously, press firmly with half a bowl of hot dough.