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Cinnabar

earth science Maturity 7-9 Next article →

Cinnabar is a striking mineral known for its bright scarlet to brick-red color.

cinnabar09
cinnabar09

Chemically, it is mercury(II) sulfide, represented by the formula HgS. This mineral serves two primary purposes in human history. First, it is the most common ore used for refining elemental mercury. Second, it has been a historic source for the brilliant red pigment known as vermilion. Because of its high density, it has a specific gravity of approximately 8.1. It is also relatively soft, with a Mohs hardness between 2.0 and 2.5.

The physical properties of cinnabar are driven by its internal atomic arrangement. It belongs to the trigonal crystal system and features a hexagonal crystalline lattice. This structure results in a high mean refractive index of about 3.08 for sodium light wavelengths. To put this in perspective, this index is much higher than that of a diamond, which is 2.42.

Cinnabar crystal structure
Cinnabar crystal structure

The mineral also exhibits birefringence, meaning it can split light into two rays. While most cinnabar is found in massive or granular forms, it can also appear as crystals with an adamantine luster. Some crystals may even show twinning, where two crystals grow together in a simple contact pattern.

Cinnabar typically forms through specific geological processes involving heat and water. It often occurs as a vein-filling mineral near volcanic activity or alkaline hot springs. The mineral is deposited by epithermal ascending aqueous solutions. These are warm water solutions that move upward toward the Earth's surface, far from their original igneous source. As these solutions travel through cracks in the rock, they leave behind deposits of mercury(II) sulfide. Cinnabar is often found alongside other minerals like quartz, pyrite, calcite, and stibnite.

Humans have utilized the vibrant color of cinnabar since antiquity. In the Near East, it was used as a rouge-type cosmetic. The Olmec culture in the New World and the Yangshao culture in China also used it for various purposes. In China, it was used to color stoneware and as early as the Zhou dynasty for writing on oracle bones. During the Song dynasty, a popular technique emerged using cinnabar to color lacquerware.

Chinese carved cinnabar lacquerware
Chinese carved cinnabar lacquerware

In Roman times, it was a highly valued paint for interior walls. However, Romans noticed that the pigment would darken if it was exposed to sunlight outdoors.

Many significant mining sites have provided cinnabar for thousands of years. The Almadén mine in Spain is perhaps the most famous. It was the most important deposit in the world for centuries and was used from Roman times until 2001.

Alchimia 1570 p 9
Alchimia 1570 p 9

Other notable locations include Giza in Egypt and various sites in California, such as the New Almaden Mine. Deposits are also found in Slovenia, Italy, Peru, and China. In the United States, cinnabar has been found in Nevada, Texas, and Alaska. These sites have been essential for extracting both the pigment and the metal.

Extracting elemental mercury from cinnabar requires a specific thermal process. To produce liquid mercury, or quicksilver, the crushed ore is roasted in rotary furnaces. During this heating process, the mercury separates from the sulfur. Because mercury evaporates easily, it can be collected using a condensing column.

Cinabrio Almadén 2
Cinabrio Almadén 2

Once collected, the liquid metal is often shipped in iron flasks. This method of distillation has been known for a very long time, as seen in historical records from the 16th century.

Despite its beauty, cinnabar carries significant health risks due to its mercury content. Mercury is a toxic element that can cause mercury poisoning, also known as mercurialism. This was recognized as early as ancient Rome, where it was seen as an occupational disease. Workers who mined or processed the ore often inhaled toxic fumes during the heating process. This exposure could cause shaking, loss of senses, and death.

Cinabrio Longinos
Cinabrio Longinos

In some historical mines, such as Almadén, the work was considered so dangerous it was likened to a death sentence. Today, modern industries use safer alternatives, such as resin-based polymers, to mimic the look of cinnabar pigments.

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🖼️ Images & Media (6)
File:Cinnabar crystal structure.png
Cinnabar crystal structure.png
File:cinnabar09.jpg
cinnabar09.jpg
File:Cinabrio Almadén 2.jpg
Cinabrio Almadén 2.jpg
Alchimia 1570 p 9.tif
File:Chinese carved cinnabar lacquerware.jpg
Chinese carved cinnabar lacquerware.jpg
File:Cinabrio Longinos.jpg
Cinabrio Longinos.jpg
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