Cinnabar: Red, Beautiful — and Toxic

By: Allison Troutner  | 

carved red cinnabar lacquer box
This 19th-century red cinnabar lacquer box was carved in the shape of a Chinese football (kemari). Cinnabar was used extensively in decorative items for centuries. USC Pacific Asia Museum/Getty Images

The name "cinnabar" might make you think this mineral has something to do with cinnamon. But in fact, the word is derived from the Arabic word zinjafr and the Persian word zinjirfrah, which means "dragon's blood." This mineral is certainly blood red, but from dragons, it is not! Cinnabar is born in the shallow veins of blazing volcanic rock. It has historically been used as a pigment called vermilion for millennia, but it's also known for use in traditional medicines and as the primary mineral ore of mercury, a highly toxic chemical element.

Cinnabar is also known as mercury sulfide (HgS), the primary ore of mercury and the same silver liquid in oral thermometers that parents used to check kids' temperatures. In the early 2000s, the Environmental Protection Agency (EPA) and the National Institute of Standards and Technology (NIST) phased them out in place of safer alternatives.

"Cinnabar occurs in near-surface, shallow veins [of volcanic rock], making it easy to mine," says Terri Ottaway, museum curator at the Gemological Institute of America (GIA). "It's crushed and then roasted to extract the mercury." Some mines have been in use since Roman times, Ottaway says, like those in Almadén, Spain. It's also mined around the world in Peru, Italy and the U.S. It registers 2 to 2.5 on the Mohs hardness scale. Today, cinnabar is mainly mined as a source of elemental mercury, but historically cinnabar was a valuable pigment in cultures worldwide because of its color.

 Cinnabar
Cinnabar in its natural state.
DeAgostini/Getty Images

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Vermilion: The Pigment of Blood, Victory and Success

Cinnabar can range in color from red-orange to a deep red-purple, says Ottaway. In its pigmented form, the mineral is called vermilion, derived from a Latin word for a worm or insect with a similar red color. "Vermilion paint was highly prized by Renaissance artists, although only the wealthy could afford it," Ottaway points out. In 2018, the Met held an exhibition just for ancient art colored with luscious vermilion pigment. In a blog post about the Met exhibition, Ellen Spindler wrote that cultures have mined cinnabar since the 10th millennium B.C.E. Cinnabar was used to paint human bones, as tattoo dye, as makeup, and to decorate buildings and ceramics. In the Middle Ages, it was even used as ink.

"Cinnabar was used in cosmetics as rouge in many cultures, from the Near East to the Olmec culture [an ancient Mesoamerican civilization]. As a red powder, it was used for ritual blessings and burials," explains Ottaway. "Ancient Chinese used the pigment in stoneware and pottery glazes and popularized it for making red lacquer."

It's no surprise that cinnabar's red color made it a popular representation of themes like blood, victory and success. Spindler writes that in Roman cultures, the pigment was dominant in triumphal processions. Genuine vermilion was replaced mainly by cadmium red in the 20th century because of the former's toxic relationship to mercury. Today, the Chinese make a vermilion pigment from synthetic mercuric sulfide, with no impurities and higher quality than natural cinnabar.

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Is Cinnabar Dangerous?

In cinnabar's natural mineral and pigmented form, it's not dangerous. However, when temperatures rise, it releases a mercury vapor which can be toxic if inhaled. "Mercury is toxic, but as long as the cinnabar isn't heated, the mercury is locked by the sulfur, making cinnabar low in toxicity," Ottaway explains.

Still, anyone handling any mineral, especially cinnabar, should wash their hands and exercise caution. "Sometimes cinnabar is found with droplets of native mercury, in its pure form on the surface and should not be handled because native mercury is easily absorbed by the body and is toxic," Ottaway says.

Also, cinnabar shouldn't be cut or ground without water to prevent the inhalation of particles, Ottaway adds. "Ground cinnabar should be handled with care, although ingesting small amounts is unlikely to cause harm because mercury sulfide just passes through your body unaltered," she says.

children working in vermilion factory
Children work under hazardous conditions in a factory producing sindoor Oct. 6, 2015 in Old Dhaka, Bangladesh. Sindoor or vermilion is a brilliant red or scarlet pigment originally made from the powdered mineral cinnabar. It is used for cosmetic purposes.
Zakir Hossain Chowdhury/Future Publishing via Getty Images

It's important to note that there are three types of mercury: elemental, inorganic mercury and organic mercury (methylmercury). The latter two are not formed from cinnabar. Though all three can cause mercury poisoning, organic mercury is the most toxic. It takes 1,000 times the amount of mercury from cinnabar to reach the neurotoxicity levels of methylmercury.

When mercury is inhaled in large amounts, it's hazardous. That's why the EPA and NIST pushed for phasing out mercury in household products, like glass thermometers that could be dropped and broken, exposing children to mercury poisoning. However, that event is unlikely to be fatal, especially since glass thermometers contain elemental mercury derived from cinnabar instead of the much more toxic methylmercury. It would take a lot more than a broken thermometer to cause long-term damage.

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Cinnabar in the Environment

Cinnabar, especially in small amounts, isn't harmful to adult humans. However, when released into the environment in large quantities, it can be harmful to animals and people alike, as is the case in Arkansas.

In the 1930s and '40s, Arkansas was a leader in the cinnabar mining industry. Because mercury is a bioaccumulative toxin (PBT), its concentration increases over time. In Arkansas' warm, wet weather, mines often flood. Mercury from man-made soil erosion is then released into the water sources, soil, vegetation and animals. So in 2016, researchers wanted to know if historical cinnabar mining had a lasting impact on the environment. Researchers found that accumulations of mercury were very high and potentially detrimental to wildlife and human populations alike, as noted in the mercury levels in the livers and brains of otters in Arkansas' rivers.

Today, the average person is unlikely to come into contact with cinnabar unless you're looking at a gallery of ancient art, have an heirloom or a 40-year-old thermometer, or you're using one of 40 traditional medicines, particularly in China.

Specialized gem and jewelry collectors may seek it out "for its beautiful color and fine crystals," says Ottaway. "Polished cabochons of cinnabar are sometimes seen in jewelry."

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