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Xuan Shi (Black Stone)
Salty in flavor, warm in nature, non-toxic. Primarily treats convulsions and epilepsy (seizures caused by fright or wind pathogen) in adults and children, sterility in women, cold pain in the lower abdomen, scanty essence with a heavy body sensation; taking it enables one to conceive offspring. Also known as Xuan Shui Shi (Black Water Stone), also known as Chu Shi (Place Stone). Grows on the south slope of Mount Tai. On the north slope of the mountain there is copper ore; copper is classified as female and male, with black being the male type. (Incompatible with Song Zhi [Pinus resin], Bai Shi [Platycladi Semen], and Jun Gui [Cinnamomum cassia bark].)

Tao Hongjing states: The Ci Shi (Magnetite) in the *Shen Nong Ben Cao Jing* (Divine Farmer's Materia Medica) is also named Xuan Shi. The *Bie Lu* (Additional Records) lists them as separate substances. Upon examination, since they share the alias "Chu Shi" and have similar therapeutic effects, yet differ in their cold/warm properties, affinity for copper/iron, and incompatibilities, and since common prescriptions no longer use it, nor do people recognize its form, it is unknown whether it is similar to Ci Shi. The *Tang Ben Cao* commentary notes: This substance is liquid iron solidified; however, it cannot attract needles. Its therapeutic effect is as described in the *Jing* (Classic), but inferior to Ci Shi. Ci Shi contains fine pores, which are yellow-red inside; when freshly broken, good quality Ci Shi can attract ten needles in succession and even lift and rotate a one-jin iron knife. Those without pores, glossy and purely black, are Xuan Shi, which cannot attract needles. Detailed illustrations are recorded under the entry for Ci Shi.

Lv Yan (Green Salt)
Salty, bitter, and acrid in flavor, neutral in nature, non-toxic. Primarily treats red eyes with tearing, corneal opacity (pterygium/leukoma), and dark eye discharge.

*Tang Ben Cao* commentary notes: Made by fermenting Guang Ming Yan (Bright Salt), Sha (Sand/Grit), and Chi Tong Xie (Red Copper Filings) into blocks, appearing green. Authentic Lv Yan originates from the Kingdom of Yanqi, harvested from beneath stones in water. It resembles Bian Qing (Flat Azure Mineral) and Kong Qing (Hollow Azure Mineral), and is an essential ingredient for ophthalmic preparations. (Originally attached to the preceding text.) Detailed illustrations are recorded under the entry for Shi Yan (Table Salt).

Maritime Medicines: According to the *Gu Jin Lu* (Records of Past and Present): Lv Yan grows on rocks in Persia, tasting salty and astringent. It primarily brightens vision and eliminates opacities, used for eye drops and treating infant Wugu Gan (infantile malnutrition/dysentery), though its efficacy is not long-lasting. Li Xiaobo of the Later Wei dynasty stated: Chi Yan (Red Salt), Chou Yan (Stinking Salt), Ma Chi Yan (Purslane Salt), and Bo Yan (Mottled Salt) are not table salt. Hu Yan (Barbarian Salt) treats eye pain. Comparing the above with the *Tang Ben Cao* commentary, all these descriptions refer to Lv Yan.

Ning Shui Shi (Freezing Water Stone)
Acrid and sweet in flavor, cold and greatly cold in nature, non-toxic. Primarily treats fever, accumulation of evil qi in the abdomen, skin burning like fire, irritability and fullness, relieved by drinking water. Eliminates excess heat in seasonal epidemics, latent heat in the five zang organs, stomach heat, irritability and fullness, stops thirst, reduces edema, and treats bi-syndrome (painful obstruction) in the lower abdomen. Long-term use prevents hunger. Also known as Bai Shui Shi (White Water Stone), also known as Han Shui Shi (Cold Water Stone), also known as Ling Shui Shi (Ice Water Stone). Those resembling mica and capable of splitting into layers are of superior quality; this is the essence of salt. Grows in the valleys of Changshan, and also in Zhongshui County and Handan. (Resolves Radix Euphorbiae Hussonis toxicity, incompatible with Sanguisorbae Radix.)

Tao Hongjing states: Changshan belongs to Bingzhou, Zhongshui County belongs to Hejian Commandery, and Handan is Zhao Commandery, all belonging to the Ji Province region. The land here is saline-alkaline, hence it is called the essence of salt, and when crushed, it resembles Piao Xiao (Mirabilite). When powdered Ning Shui Shi is placed in water, if it forms ice in summer, it is considered excellent. *Tang Ben Cao* commentary: There are two types of this stone, those with longitudinal grain and those with transverse grain; clear and transparent ones are superior. Some say longitudinal grain is Han Shui Shi, while transverse grain is Ning Shui Shi. Currently, those from Hancheng in Tongzhou are yellowish-green with mica-like grain, which is good; those from Chengcheng have diagonal grain and are white, which is inferior. Ministers Yu Xi et al. carefully followed Wu Shi’s notes: Shen Nong said acrid; Qi Bo, Yi He, and Bian Que said sweet, non-toxic; Ji Shi said greatly cold. Some grow in Handan. Harvest time is unspecified; color resembles mica. *Yao Xing Lun* (Discussion on Drug Properties) states: Han Shui Shi can suppress Dan Shi (cinnabar pill) toxic wind, remove mental restlessness, thirst, and stuffiness, and resolve relapse after recovery from Shang Han (Cold Damage).

Tu Jing says: Ning Shui Shi is Han Shui Shi, growing in Changshan valleys, and also in Zhongshui County and Handan. Currently available in Fen and Xi Prefectures in Hedong, and Deshun Army. There are two types: those with longitudinal grain and those with transverse grain. Clear and transparent like splittable mica, when thrown into water, takes on the water's color; if the water appears frozen/still, it is superior. Some say longitudinal grain is Han Shui Shi, transverse grain is Ning Shui Shi. Harvested in March. There is another type called Leng You Shi (Cold Oil Stone), completely similar to this, except that when thrown into boiling oil, the oil cools down. This stone is toxic; if mistakenly used, it causes inability to move the waist and below.

Lei Gong says: For processing, first boil in fresh ginger juice until the juice is exhausted, then finely grind into powder for use. For every ten liang processed, use one yi of ginger juice.

Empirical Formula: Treats infant Dan Du (erysipelas), with hot and red skin. Use half a liang of Han Shui Shi and one part Bai Tu (White Clay), pound and sieve into powder, mix with rice vinegar, apply topically for cure.

Ji Ri (Note: Text fragment, likely a book/formula name): In a clean pit, cover with a basin, surround with wet soil, leave overnight, then take out. Add two liang each of Gan Cao (Licorice Root) powder and Tian Zhu Huang (Bambusa Textilis Calamus), and two fen of Long Nao (Borneol). Mix with glutinous rice paste to make pills the size of bullet seeds, take with honey-water solution.

Shang Han Lei Yao (Essentials of Cold Damage): Treats Rou Dan (muscular jaundice/swelling), where urine is white. Use Ning Shui Shi as the main herb.

Dan Fang Jing Yuan (Mirror Source of Alchemical Furnaces): Ning Shui Shi can be made into oil coatings, is edible, and is used to refine Cinnabar into Kui Fu Xuan Jing.

Yan Yi says: Ning Shui Shi, also called Han Shui Shi, has clear and penetrating grain texture. Some carve it into pillows for use in summer. For medicinal use, it must be calcined. However, merchants may calcine it and mix in lead white (basic lead carbonate) to pass it off as genuine; this must be carefully distinguished. Tao Hongjing stated: Those that form ice in summer are excellent. If this were true, none could be found in the world, suggesting his statement was erroneous.