亦名寒水石。即盐精石。（一名泥精。昔人谓之盐枕。今人谓之盐根。）生于
卤地积盐之下。
大块有齿棱。如马牙硝。清莹如水晶。亦有带青黑色者。打破皆方。暑月回润。入水浸
久亦化。苏颂注元精石。谓解池有盐精石。味更咸苦。乃元精之类。固是物也。（濒湖）
寒水石有二。一是软石膏。一是凝水石。唐宋以来。诸家不详本文盐精之说。遂误以石
膏方解石为寒水石。而盐精之寒水绝不知用。此千载之误也。然则古方所用寒水石。正即此
种凝水石。唐宋诸方寒水石是石膏。近方寒水石则是长石方解石耳。（参用濒湖）
味辛咸甘。气大寒。本经主治身热。腹中积聚邪气。皮中如火烧。烦满。（水饮之）除
时气热盛。五脏伏热。胃中热。止渴凉血。降火止牙疼。坚牙明目。入肾走血。除热之功。
同于诸盐。经曰。小热之气。凉以和之。大热之气。寒以取之。又曰。热淫于内。治以咸寒。
凝水
〔论〕 苏氏以凝水石为元精之类。而东璧氏遂无分别。今细绎之。同中觉有异处。观
二石之释名。同禀水气。而凝水止曰寒水。元精则曰太乙元精。同为盐结。而凝水止曰盐精。
元精则曰阴精。岂得谓无少异乎。说见元精石条。能除有余邪热。凡阴虚火旺。咳嗽吐血多
痰。潮热骨蒸。并脾胃作泻者。慎弗误服。（仲淳）
〔修治〕 每凝水十两。须用生姜二十两捣取自然汁煮干。研粉用。
Also known as Hanshui Shi (Cold Water Stone). It is Yanjing Shi (Salt Essence Stone). (Another name is Nijing; ancient people called it Yanzhen [Salt Pillow]; modern people call it Yangen [Salt Root].) It grows beneath accumulated salt in saline lands.
Large pieces have tooth-like ridges. They resemble Mayaxiao (Natrii Sulfas crystallized). The texture is clear and lustrous like crystal. Some also have bluish-black colors. When broken, the cross-section is square. During hot summer months, they become moist again. If soaked in water for a long time, they also dissolve. Su Song's commentary on Yuanjing Shi states that there is Yanjing Shi in the salt pools of Jiezhou, with a taste even more salty and bitter, belonging to the category of Yuanjing. Indeed, it is this substance. (Li Shizhen)
There are two types of Hanshui Shi: one is Ruan Shigao (Soft Gypsum), and the other is Ning Shui Shi (Condensed Water Stone). Since the Tang and Song dynasties, various authors failed to carefully examine the original text's explanation of "Yanjing," thereby mistakenly using Shigao Fangjieshi (Gypsum Fibrosum/Fibrous Gypsum) as Hanshui Shi, while completely unaware of how to use the true Hanshui Shi which is Yanjing. This is an error spanning a millennium. Therefore, the Hanshui Shi used in ancient prescriptions is precisely this type of Ning Shui Shi. In Tang and Song dynasty prescriptions, Hanshui Shi referred to Shigao (Gypsum Fibrosum); in recent prescriptions, Hanshui Shi refers to Changshi Fangjieshi (Feldspar/Spar). (Referencing Li Shizhen)
Taste: Pungent, Salty, Sweet. Nature: Greatly Cold. The *Shennong Bencao Jing* indicates its indications include body heat, accumulation of pathogenic qi in the abdomen, a sensation of burning fire in the skin, and vexation and fullness. (Caused by fluid retention.) It eliminates excessive heat from seasonal pathogens, latent heat in the five zang organs, heat in the stomach, stops thirst, cools blood, descends fire, stops toothache, strengthens teeth, improves vision, enters the Kidney channel, and moves in the blood level. Its efficacy in clearing heat is similar to that of various salts. The classic states: For mild heat conditions, use cool properties to harmonize; for severe heat conditions, use cold properties to eliminate. It also states: When heat invades internally, treat with salty-cold agents.
Ning Shui Shi
[Discussion] Su Song considered Ning Shui Shi to be of the same category as Yuanjing, and Dongbi (Li Shizhen) subsequently made no distinction between them. Upon careful examination now, differences can be perceived amidst their similarities. Observing the etymology of these two stones, both inherit the Qi of Water, yet Ning Shui is only called Hanshui, whereas Yuanjing is called Taiyi Yuanjing. Both are formed from salt crystallization, yet Ning Shui is only called Yanjing, whereas Yuanjing is called Yinjing. How can one say there is no slight difference? Detailed explanations are found under the entry for Yuanjing Shi. It can eliminate excess pathogenic heat. For cases of Yin deficiency with Fire hyperactivity, coughing with hemoptysis and profuse phlegm, tidal fever with bone-steaming sensation, and diarrhea caused by Spleen and Stomach dysfunction, one must be cautious not to take it erroneously. (Zhongchun)
[Processing] For every ten taels of Ning Shui Shi, twenty taels of fresh ginger must be crushed to extract natural juice, and the stone boiled in this juice until dry, then ground into powder for use.