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[Shennong Bencao Jing, Middle Grade]
By rubbing an iron needle with magnetite (Cishi), the needle points south. This reflects the hexagram Ji Ji (After Completion / Water and Fire in their proper places), serving as a sign of the interaction between Water and Fire. The transformation from lifeless matter to responsive entity follows natural principles.

[Flavor and Toxicity] Acrid, Cold, Non-toxic.

[Indications] Primarily treats generalized Bi syndrome (Zhou Bi) caused by Wind-Dampness, pain in the limbs and joints, inability to hold objects, a sensation of coldness and soreness/aching throughout the body, severe heat with vexation and fullness, and deafness.

[Verification] It is stated: Magnetite grows in the valleys of Mount Tai and on the shady slopes of Mount Ci. Where iron deposits exist, its Yang energy is generated. It is also found in modern Xuzhou and mountains near the South Sea.

Magnetite from Cizhou offered as tribute is the best; it can attract iron, suspending dozens of iron pieces or even knives and utensils weighing one or two jin, rotating without falling. Such quality is superior. There is no fixed time for harvesting. Stones with pores containing yellow-red substances and fine hairs on top have even better efficacy. *Nanchuan Yiwu Zhi* states: At Qitou in the Rising Sea, where waters are shallow, there is much magnetite and Zhongma stone. Both stones resemble magnetite but cannot attract iron. Zhongma stone has a redder core and rough skin; it is Iron Mountain Stone. Ingestion causes malignant sores that are incurable. A piece of true magnetite capable of attracting one jin of iron is called "Yannian Sha" (Longevity Sand); one attracting eight liang is called "Xucail Shi"; one attracting five liang is called "Cishi" (Magnetite). Rubbing a needle tip with magnetite makes it point south. The method involves taking a single thread from new cotton wadding, attaching it to the middle of the needle with wax the size of half a mustard seed, and hanging it in a windless place; the needle will consistently point south. Alternatively, threading the needle horizontally through a rush pith and floating it on water also results in it pointing south. This demonstrates the principle of physical resonance. *Tusu Zhenjun* states: When iron first receives Qi from the Sun, Luoshi (Halite/Niter) is produced initially. After 150 years, it becomes magnetite, and after another 200 years, it matures into iron. To process one jin of magnetite, use Wuhua Pi (Bark of Five-Flowered Tree) and Diyu (Sanguisorbae Radix), each one yi (an ancient weight unit), along with fifteen liang of silk floss. Chop all three together. Pound them into 20-30 pieces on a stone. Place the stone in a porcelain bottle, add herbal medicines below, and boil in flowing water from the east for three days and nights. Remove, wipe dry, wrap in cloth, pound finely again, then grind into dust. Process using the water flotation method (Shuifei), then grind again for use. Bupleuri Radix (Chaihu) acts as an assistant drug, neutralizing iron toxicity and resolving metal-related issues. It is incompatible with Peony Root (Mudanpi) and Aconitum Lateralis Preparatum (Mangcao - note: context implies toxic herb incompatibility), and fears Huangshizhi (Yellow Earth Resin).

[Commentary] It is stated: Initially, Luoshi is produced, which over time matures into iron. Magnetite is the mother; iron is the child. Magnetite and iron inhale and exhale each other's Qi. Though lifeless, they possess a form of sentiment, and their energies resonate mutually. Thus, they treat generalized Bi syndrome due to Wind-Dampness, dampness flowing into limb joints causing pain, coldness, and soreness, inability to hold objects (indicating the hand's failure to perceive objects), and inability to hear sounds (indicating the ear's failure to perceive sounds). By analogy, this extends to treating eyes failing to perceive colors, noses failing to perceive odors, tongues failing to perceive tastes, and conditions like carbuncles, scrofula, cervical lymphadenopathy, and throat pain where the body fails to perceive touch. These are all analogical applications. Generally, severe heat is the cause, and vexation/fullness is the manifestation. Magnetite belongs to the Eight Minerals associated with Water and is located in the Kan trigram. It treats these conditions through counteracting methods; thus, Cold, Heat, Warmth, and Coolness act inversely.