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[Shigao (Gypsum Fibrosum)]
Taste: Acrid, Sweet. Nature: Cold, Non-toxic. Meridians Entered: Lung, Stomach.
Indications: Primarily induces sweating to release the muscle layer (releasing exterior pathogens from the muscular level), soothes the Spleen Qi, generates fluids and quenches thirst, clears Stomach heat and eliminates phlegm, and is particularly effective for treating headaches. Its efficacy resembles that of Fajieshi (Calcitum). Authentic Shigao must be translucent and crystal-clear like rock crystal. Egg white is used as an adjuvant. It is incompatible with Mangcao (Aristolochia Manshuriensis Root), Mumingdugong (likely a specific toxic plant/mineral), Badou (Crotonis Fructus), and fears iron.

Commentary: The acrid taste of Shigao disperses and enters the Lung; the sweet taste moderates and enters the Stomach, thus it possesses dispersing properties. Zhang Zhongjing named it "Baihu" (White Tiger), which implies two meanings: first, because it enters the Lung meridian (Lung corresponds to Metal and the White Tiger in Five Elements theory); second, because its medicinal nature is vigorous and potent. If misused in patients with weak Stomach Qi unable to eat, or those with fever due to Blood deficiency, it can cause significant harm.

Leigong stated: When using Shigao, do not use Fajieshi (Calcitum). Although this stone is white, it is not transparent and has a drying nature. Shigao from Yiqingshan, Ruoshan County, Yanzhou Prefecture, is crystal clear like rock crystal and has a mild, benign nature. To process it, first crush it into powder in a stone mortar, sift it through fine silk gauze, then perform water flotation (a purification method involving grinding with water and separating fine particles) with raw Gancao (Licorice Root Decoction). Remove the water, dry it, and grind it again until extremely fine for optimal use.

[Qingyan (Natrii Chloridum Viride / Blue Salt)]
Taste: Salty. Nature: Cold, Non-toxic. Meridians Entered: Kidney.
Indications: Improves vision, relieves pain, benefits Qi, strengthens sinews and bones, assists the Water Organ (Kidney), eliminates epigastric and abdominal pain, breaks up accumulations, and treats tinea and scabies sores. Also known as Rongyan, also known as Huyan.

Commentary: Qingyan tastes salty, which is suitable for the Kidney; therefore, it enters the Kidney meridian exclusively. Once the Water Organ (Kidney) is tonified, what is surprising about its abilities to improve vision and strengthen bones?

[Yanshi (Natrii Chloridum / Table Salt)]
Taste: Salty. Nature: Warm, Non-toxic. Meridians Entered: Kidney, Lung, Liver.
Indications: Treats poisoning from Gui Gu Xie Zhu Du Wa (toxins caused by abnormal qi or parasites), washes lower body ulcers, induces vomiting to expel Tan Pi (phlegm-rheum accumulation in the middle jiao), hot compresses to treat hernia and gather Kidney Qi, stops Huoluan (cholera-like syndrome) and sudden epigastric/abdominal pain, kills parasites, dispels wind, improves vision, and strengthens teeth. The whiter, resembling frost or snow, the better. Use after stir-frying and grinding.

Commentary: The salty flavor of Yanshi naturally belongs to the Kidney Fu organ. The Lung is the Mother of the Kidney, and the Liver is the Child of the Kidney; therefore, it enters these three meridians. The Ben Cao (Materia Medica) states: "Excessive consumption damages sinews, harms the Lung and Water metabolism, causing edema and cough; it is contraindicated in Blood deficiency." Why is this? Because the salty flavor travels to the Kidney. Excessive intake overwhelms the Kidney, causing injury. This subsequently steals Qi from the Mother organ (Lung), damaging Lung Qi. Damaged Lung Qi leads to Metal overacting on Wood, affecting the Liver. Since the Liver governs sinews and stores Blood, and the Lung governs cough and produces Water, how can one avoid these syndromes?