\r凝水石\ph31.bmp\r，即寒水石也，生常山山谷，又出中水县及邯郸。今河东汾、隰
州及德顺军亦有之。
此有两种，有纵理者，有横理者，色清明如云母可析，投置水中，与水同色，其水凝动者为
佳。或曰纵理者为寒水石，横理者为凝水石。三月采。又有一种冷油石，全与此相类，但投
沸油铛中，油即冷者，是也。此石有毒，若误用之，令腰以下不能举。
\r石膏\ph32.bmp\r，生齐山山谷及齐卢山、鲁蒙山，今汾、孟、虢、耀州、兴元府亦
有之。生于山石上，
色至莹白，其黄者不堪。此石与方解石绝相类，今难得真者。用时，惟取未破者以别之。其
方
解石，不附石而生，端然独处，外皮有土及水苔色，破之皆作方棱。石膏自然明莹如玉石，
此为异也。采无时。方解石，旧出下品。《本经》云∶生方山。陶隐居以为长石，一名方石
，疗体相似，疑是一物。苏恭云∶疗热不减石膏，若然似可通用，但主头风不及石膏也。又
今南方医家着一说云∶按本草石膏、方解石，大体相似。但方解石不因石端然独处。又云∶
今市人皆以方解石代石膏，未见有真石膏也。又陶隐居谓石膏皆在地中，雨后时时自出，取
之皆如棋子，此又不附石生也。二说相反，未知孰是。今详石膏，既与方解石肌理、形段、
刚柔皆同，但以附石、不附石，岂得功力相异也。但意今之所用石膏、方解者，自是方解石
，石膏乃别是一物尔。今石膏中时时有莹澈可爱，有纵理而不方解者，好事者或以为石膏。
然据本草，又似长石。又有议者，以谓青石间往往有白脉贯澈类肉之有膏肪者，为石膏。此
又本草所谓理石也。然不知石膏定是何物。今且依市人用方解石。然博物者，亦宜坚考其实
也。今密州九仙山东南隅地中，出一种石，青白而脆，击之内有火，谓之玉火石，彼土医人
常用之。云味甘、微辛，温。疗伤寒发汗，止头目昏眩痛，功与石膏等。彼土人或以当石膏
，故以附之。
Ningshui Shi (Condensing Water Stone), also known as Hanshui Shi (Cold Water Stone), grows in the valleys of Changshan, and is also produced in Zhongxian County and Handan. Currently, it is also found in Fenzhou and Xizhou of Hedong Circuit, and Deshun Jun.
There are two types of this stone: one with longitudinal grain and one with transverse grain. Its color is clear and bright like mica, allowing it to be split; when thrown into water, it takes on the same color as the water, and the type that causes the water to appear congealed or rippling is considered superior. Some say the longitudinal-grained variety is Hanshui Shi, while the transverse-grained variety is Ningshui Shi. It is harvested in the third month. There is another type called Lengyou Shi (Cold Oil Stone), which is entirely similar to this but turns oil cold when thrown into a wok of boiling oil; this refers to that substance. This stone is toxic; if mistakenly used, it can cause paralysis from the waist down.
Shigao (Gypsum Fibrosum) grows in the valleys of Qishan, as well as Qilushan and Lumengshan. Currently, it is also found in Fenzhou, Mengzhou, Guozhou, Yaozhou, and Xingyuan Fu. It grows upon mountain rocks, with a color that is extremely translucent white; those that are yellow are unsuitable for use. This stone is extremely similar to Fangjie Shi (Calcitum), making it difficult nowadays to obtain genuine Shigao. When using it, only unbroken pieces should be selected for differentiation. Fangjie Shi does not grow attached to rock but stands upright alone; its outer skin has the color of soil and aquatic moss, and when broken, it forms square edges. Shigao is naturally bright and translucent like jade, which is the difference. It can be harvested at any time. Fangjie Shi was previously listed in the inferior category. The *Shennong Bencao Jing* states it grows in Fangshan. Tao Hongjing believed it to be Changshi (Long Stone), also named Fangshi, noting their therapeutic properties are similar and suspecting they might be the same substance. Su Gong stated that its ability to treat heat is no less than Shigao; if so, they might be interchangeable, though it is inferior to Shigao in treating head wind. Furthermore, some southern physicians currently propose that according to herbal texts, Shigao and Fangjie Shi are largely similar. However, Fangjie Shi does not stand upright independently without attaching to rock. They also claim that merchants today substitute Fangjie Shi for Shigao, and true Shigao is rarely seen. Additionally, Tao Hongjing mentioned that Shigao grows underground and emerges spontaneously after rain, resembling chess pieces, which implies it does not grow attached to rock. These two theories contradict each other, and it is unknown which is correct. Upon detailed examination, since Shigao shares the same texture, shape, and hardness/softness as Fangjie Shi, how can their efficacy differ merely because one attaches to rock and the other does not? It is my opinion that what is currently used as Shigao or Fangjie Shi is actually Fangjie Shi, whereas Shigao is a distinct substance. In current Shigao samples, there are often pieces that are crystal clear and lovely, with longitudinal grain but not square-edged; collectors sometimes pass these off as Shigao. However, according to herbal records, they resemble Changshi. Another view suggests that within blue stones, white veins penetrating clearly, resembling fat within meat, constitute Shigao. This corresponds to the Lizhi (Marble) mentioned in herbal texts. Thus, it remains unclear what Shigao definitively is. For now, we follow the market practice of using Fangjie Shi. However, scholars of natural history should rigorously verify its true nature. Currently, in the southeastern corner of Jiuxian Mountain in Mizhou, a stone is unearthed from the ground; it is blue-white and brittle, emitting sparks when struck, known as Yuhuoshi (Jade Fire Stone). Local physicians frequently use it. It is said to have a sweet taste, slightly pungent, and warm nature. It treats shanghan (cold damage) by inducing sweating and stops dizziness and pain in the head and eyes, with efficacy equal to Shigao. Locals sometimes use it as Shigao, so it is appended here.