性凉无毒，味与经络，诸书不载。主五淋小便不利，肠风痔 。妇人产难，两手各握一
枚，立验。研细水飞用。
按∶《图经》云∶石燕出零棱郡，今祁阳县沙滩亦有之，形似蚶而小，其实石也。观其
主治，都是行下之功，食疗赞其补益，似未然耳。
味辛咸，性寒无毒，入肾经。主周身湿痹，肢节中痛，目昏耳聋，补劳伤，除烦躁消肿
毒，令人有子。能吸重铁者佳，入火 红，醋淬七次，研绝细用。柴胡为使，恶牡丹，芥草，
黄石脂。
按∶磁石入肾，何也？盖以性能引铁，取其引肺金之气入肾，使子母相生尔，水得金而
清，则相火不攻自去，故主治如上。然久服多服，必有大患，勿喜其功而忽其害也。
雷公云∶凡使勿误用玄中石并中麻石，此二石真相似磁石，只是吸铁不得。中麻石心有
赤，皮粗。是铁山石也。误服之，令人生恶疮，不可疗。磁石一片，四面吸铁一斤者，此名
延年沙。四面吸得铁八两者，号曰续采石。四面吸得五两上下者为磁石。凡修事一斤，用五
花皮一镒，地榆一镒，故悬十五两，二件并细锉，于石上捶碎，作二三十块，半磁石入磁瓶
中，下草药，以东流水煮三日夜，漉出拭干，以布裹之，向大石上再捶，令细，入乳钵中，
研极细如尘，以水飞过，又研如粉用之。
石燕：
药性凉，无毒。其味道及归经，各类医书均未记载。主要治疗五种淋证（以小便频数短涩、滴沥刺痛为主症的疾病）导致的小便不通利，以及肠风痔漏（因风邪侵袭肠道引起的痔疮出血或肿痛）。妇女难产时，双手各握一枚石燕，可立即见效。使用时需研成细粉，用水飞法（将药物与水共研，利用粗细粉末在水中的悬浮性不同进行分离提纯的方法）处理。
按语：《本草图经》记载：石燕产于零陵郡，如今祁阳县的沙滩上也有出产，形状像蚶（一种贝类）但较小，实际上是石头。观察它的主治功效，都是下行通利的作用，食疗书籍称赞它有补益作用，似乎并不准确。
磁石：
味辛、咸，药性寒，无毒。入肾经。主要治疗周身风湿痹痛（风寒湿邪闭阻经络引起的肢体关节疼痛、麻木、重着等症状），四肢关节疼痛，视物昏花，听力减退，补益虚劳损伤，消除烦躁和肿胀毒气，有助于生育。能吸附沉重铁块的磁石为佳。使用时放入火中烧红，用醋淬炼七次，研磨至极细后使用。以柴胡为引经药，忌与牡丹、芥草、黄石脂同用。
按语：磁石为何入肾经呢？因为其性能吸引铁，取象比类，认为它能引导肺金之气进入肾水，使母子相生（金生水）。水得到金的清肃之气则变得清澈，相火（寄居于肝肾的生理之火）不攻自退，所以主治上述病症。然而长期服用或多服，必然带来大患，不要只喜欢它的功效而忽视它的危害。
雷公云：凡是使用磁石，不要误用玄中石和中麻石，这两种石头与磁石非常相似，只是不能吸铁。中麻石中心有红色，外皮粗糙，这是铁山石。误服后会让人长出恶疮，无法治愈。磁石一片，四面能吸附一斤铁的，名叫“延年沙”；四面能吸附八两铁的，称为“续采石”；四面能吸附五两左右的，才是磁石。凡是炮制一斤磁石，需用五花皮一镒（古代重量单位，约合二十两或三十两，此处指一定分量），地榆一镒，将它们悬挂起来，连同十五两磁石一起，把草药切碎，在石头上捶碎，分成二三十块，将一半磁石放入磁瓶中，下面放草药，用东流水煮三天三夜，捞出擦干，用布包裹，再在大石头上捶打，使其变细，放入乳钵中，研磨得极细如灰尘，用水飞法处理，再次研磨成粉后使用。
Shiyan (Lithornithidae Fossil):
The nature is cool, and it is non-toxic. Its flavor and meridian tropism are not recorded in various medical texts. It primarily treats urinary difficulty caused by the five types of strangury (a syndrome characterized by frequent, urgent, and painful urination), as well as intestinal wind and hemorrhoids (hemorrhoidal bleeding or swelling/pain caused by wind pathogen invading the intestines). For difficult labor in women, holding one piece in each hand yields immediate results. When used, it should be ground into a fine powder and processed by water levigation (a purification method utilizing the difference in suspension properties of coarse and fine particles in water).
Commentary: *Bencao Tujing* records that Shiyan originates from Lingling Commandery, and today it can also be found on the beaches of Qiyang County. Its shape resembles a clam but is smaller; it is actually stone. Observing its therapeutic effects, they are all functions of descending and unblocking. Dietary therapy books praise its tonifying benefits, which seems inaccurate.
Cishi (Magnetite):
The flavors are pungent and salty; the nature is cold, and it is non-toxic. It enters the Kidney Meridian. It primarily treats generalized rheumatic bi-syndrome (pain, numbness, and heaviness in limbs and joints caused by obstruction of meridians by wind-cold-damp pathogens), pain in the limbs and joints, blurred vision, deafness, tonifies deficiency and injury, eliminates irritability and swelling/toxins, and facilitates fertility. Magnetite that can attract heavy iron is considered superior. When used, it is heated red-hot in fire, quenched in vinegar seven times, and ground to an extremely fine consistency before use. Chaihu (Bupleuri Radix) serves as a guiding herb. It is contraindicated with Mudanpi (Moutan Cortex), Jiecao, and Huangshizhi.
Commentary: Why does Cishi enter the Kidney Meridian? Because its nature allows it to attract iron, by analogy, it is believed to guide the Qi of Lung Metal into Kidney Water, promoting the mutual generation of mother and child (Metal generates Water). When Water receives the clarifying energy of Metal, it becomes clear, and the Ministerial Fire (physiological fire residing in Liver and Kidney) retreats without attack. Hence, it treats the aforementioned conditions. However, long-term or excessive consumption will inevitably lead to serious harm; do not favor its efficacy while ignoring its dangers.
Leigong states: When using Cishi, do not mistakenly use Xuanzhongshi or Zhongmashi. These two stones resemble Cishi closely but cannot attract iron. Zhongmashi has a red center and rough skin; it is Iron Mountain Stone. Ingestion causes malignant sores that are incurable. A piece of Cishi that attracts one jin (approx. 500g) of iron from all four sides is named "Yannian Sha" (Longevity Sand); one that attracts eight liang (approx. 375g) is called "Xucail Shi"; one that attracts around five liang (approx. 250g) is true Cishi. For processing one jin of Cishi, use one yi (an ancient weight unit) of Wuhua Pi and one yi of Duyu. Suspend them together with fifteen liang of Cishi. Finely chop the herbs, crush them on a stone into twenty to thirty pieces, place half of the Cishi into a magnetic bottle, put the herbs underneath, and decoct in running water from the east for three days and nights. Remove, wipe dry, wrap in cloth, and hammer again on a large stone until fine. Place in a mortar, grind until extremely fine like dust, process by water levigation, and grind again into powder for use.