Cinnabar

Cinnabar typically has a Mohs hardness of 2.0-2.5, making it quite soft. Its color is distinctively vermillion red to brownish-red. The luster can range from adamantine (diamond-like) when pure to sub-metallic or dull in massive forms. It crystallizes in the trigonal crystal system, often forming rhombohedral crystals, though it is more commonly found as granular, massive, or earthy aggregates. Cinnabar has perfect prismatic cleavage in three directions. Its specific gravity is very high, ranging from 8.0 to 8.2.

Cinnabar forms in low-temperature hydrothermal veins associated with volcanic activity and hot springs. It also occurs in sedimentary rocks near recent volcanic activity where mercury-rich fluids deposit the mineral. Its formation often happens at depths of less than a few hundred meters. Geological age varies as it forms in active geothermal systems, so it can be relatively recent (Cenozoic to modern).

Historically, cinnabar was the primary ore for mercury extraction, which was used in thermometers, barometers, and electrical switches. Its vibrant red color led to its use as a pigment (vermilion) in paints, cosmetics, and art for millennia, though its use as a pigment has significantly decreased due to its toxicity. It's also collected by mineral enthusiasts for its striking color and crystal forms.

Cinnabar is perhaps best known for being the most common ore of mercury. The name 'cinnabar' is believed to come from the ancient Greek 'kinnabari' referring to a red pigment. Due to its mercury content, handling cinnabar dust or heating it can release toxic mercury vapor, posing health risks. Ancient civilizations, including the Romans and ancient Chinese, extensively mined cinnabar for its pigment and mercury.

In the field, cinnabar is easily identified by its distinctive vermillion red color, high density (it feels heavy for its size), and relatively low hardness. It often occurs in veins or as disseminated grains in host rocks. Common locations include Almadén, Spain (historically the largest mercury mine), Idrija, Slovenia; New Almaden, California, USA; various locations in China; and mines in Peru and Mexico. When identifying, its red streak is also a key indicator. Collectors should be aware of its toxicity and handle it with care, avoiding inhalation of dust or prolonged skin contact.