Cinnabar: Vibrant, Stunning — Yet Hazardous

The term "cinnabar" might evoke thoughts of cinnamon, but its origins trace back to the Arabic zinjafr and Persian zinjirfrah, meaning "dragon's blood." True to its name, this mineral boasts a deep red hue, though it has no connection to dragons. Formed in the shallow veins of volcanic rock, cinnabar has been prized for centuries as the source of vermilion pigment. It also played a role in traditional medicine and is the principal ore of mercury, a highly poisonous element.

Cinnabar, scientifically known as mercury sulfide (HgS), is the main source of mercury, the same silvery liquid once found in oral thermometers. By the early 2000s, the EPA and NIST had discontinued their use, replacing them with safer options.

"Cinnabar is found in shallow veins close to the surface of volcanic rock, making it easily accessible for mining," explains Terri Ottaway, curator at the Gemological Institute of America (GIA). "The mineral is crushed and then heated to release mercury." Ottaway notes that some mines, such as those in Almadén, Spain, have been operational since Roman times. Cinnabar is also extracted in Peru, Italy, and the U.S. It scores between 2 and 2.5 on the Mohs hardness scale. While modern mining focuses on extracting mercury, historically, cinnabar was prized globally for its vibrant pigment.

Vermilion: The Pigment of Blood, Victory and Success

Cinnabar exhibits a spectrum of hues, from reddish-orange to a rich purplish-red, according to Ottaway. When processed into pigment, it is known as vermilion, a term rooted in Latin, referring to a similarly colored insect. "Renaissance artists highly valued vermilion paint, though its cost limited its use to the affluent," Ottaway remarks. In 2018, the Met hosted an exhibition showcasing ancient artworks adorned with this vibrant pigment. In a blog post about the exhibition, Ellen Spindler highlighted that cinnabar mining dates back to 10,000 B.C.E. It was used to color bones, as tattoo ink, cosmetics, and for decorating structures and pottery. During the Middle Ages, it even served as writing ink.

"Cinnabar served as a cosmetic rouge across various cultures, from the Near East to the ancient Olmec civilization of Mesoamerica. It was also used as a red powder for ceremonial blessings and burial rites," says Ottaway. "The ancient Chinese incorporated the pigment into stoneware and pottery glazes, and it became widely known for creating red lacquer."

Given its vivid red hue, cinnabar naturally symbolized themes like blood, triumph, and prosperity. Spindler notes that in Roman traditions, the pigment was prominently featured in victory processions. By the 20th century, genuine vermilion was largely replaced by cadmium red due to its mercury-related toxicity. Today, the Chinese produce a synthetic mercuric sulfide pigment, free of impurities and of superior quality compared to natural cinnabar.

Is Cinnabar Dangerous?

In its natural mineral or pigmented state, cinnabar is not hazardous. However, when exposed to heat, it emits mercury vapor, which can be harmful if inhaled. "Mercury is toxic, but as long as cinnabar remains unheated, the sulfur binds the mercury, rendering it minimally toxic," Ottaway clarifies.

Nevertheless, anyone handling minerals, particularly cinnabar, should wash their hands and proceed with care. "Occasionally, cinnabar is found with droplets of pure mercury on its surface, which should not be touched, as mercury is readily absorbed by the body and is poisonous," Ottaway warns.

Ottaway also advises against cutting or grinding cinnabar without water to avoid inhaling its particles. "While ground cinnabar should be handled cautiously, consuming small quantities is generally harmless, as mercury sulfide passes through the body unchanged," she explains.

It’s crucial to understand that mercury exists in three forms: elemental, inorganic, and organic (methylmercury). The latter two are not derived from cinnabar. While all three can lead to mercury poisoning, organic mercury is the most dangerous. It requires 1,000 times the amount of mercury from cinnabar to match the neurotoxicity levels of methylmercury.

Inhaling large quantities of mercury is highly dangerous. This is why the EPA and NIST advocated for removing mercury from household items, such as glass thermometers, which could break and expose children to mercury poisoning. However, such incidents are rarely fatal, especially since glass thermometers contain elemental mercury sourced from cinnabar, not the far more toxic methylmercury. A broken thermometer alone is unlikely to cause lasting harm.

Cinnabar in the Environment

While cinnabar poses little risk to adults in small quantities, its release into the environment in large amounts can be detrimental to both animals and humans, as seen in Arkansas.

During the 1930s and 1940s, Arkansas was a major player in cinnabar mining. Mercury, a persistent bioaccumulative toxin (PBT), becomes more concentrated over time. In Arkansas' warm, humid climate, mines frequently flooded, releasing mercury from soil erosion into water sources, soil, plants, and animals. In 2016, researchers investigated whether historical cinnabar mining had long-term environmental effects. They discovered dangerously high mercury levels, particularly in the livers and brains of otters in Arkansas' rivers, posing risks to both wildlife and humans.

Nowadays, the average person is unlikely to encounter cinnabar unless they are viewing ancient art, own an heirloom or an old thermometer, or use one of 40 traditional medicines, especially in China.

Ottaway notes that specialized gem and jewelry enthusiasts may pursue cinnabar "for its striking color and exquisite crystals." She adds, "Polished cinnabar cabochons occasionally appear in jewelry pieces."