Cinnabar
Mercury(II) Sulfide var. Cinnabar · Mineral Specimen / Collector Mineral / Toxic Heavy Metal Ore
Crystal System
Trigonal system; commonly occurs in massive, granular, or earthy forms, but also as rhombohedral crystals and twins.
Mineral Group
Sulfides
Chemical Formula
HgS (Mercury Sulfide)
Formation Process
Hydrothermal formation occurring at low temperatures in veins and impregnation deposits near recent volcanic activity or hot springs.
About This Crystal
Deep cochineal-red to brownish-red color with an adamantine luster in crystalline forms or a dull, earthy luster in massive forms. Transparent to opaque with a high refractive index.
Physical Characteristics
Color: Vermilion red; Streak: Scarlet; Cleavage: Perfect rhombohedral; Fracture: Subconchoidal to uneven; Specific Gravity: 8.1; Luster: Adamantine to dull.
Optical Properties
Uniaxial positive; Refractive Index: 2.905 – 3.256; Extreme birefringence (0.351); No pleochroism; Distinctive red internal reflections.
Hardness & Durability
Origin Region
Almadén (Spain), Huancavelica (Peru), Guizhou and Hunan (China), and various hydrothermal deposits in the United States and Italy.
Hardness & Durability
Mohs hardness: 2.0 – 2.5 (very soft). Extremely fragile and brittle with high sensitivity to heat and light. Not suitable for jewelry.
Care & Maintenance
Handle with gloves due to mercury content; store in airtight containers away from heat or direct sunlight (light can cause surface darkening/metacinnabar transition). Clean only with dry, soft brushes.
Rarity & Value
Relatively rare in high-quality crystal form. Value depends on color saturation and crystal size. Primarily valued as the main ore of mercury and for historical pigment use.
Special Characteristics
Known for its extreme density and high refractive index. Exhibits photosensitivity where specimens can darken over time when exposed to UV light.
Lore & History
Historically used as the pigment 'Vermilion' in ancient art and cosmetics. In alchemy, it was considered the source of mercury. Historically significant in Chinese culture for lacquerware and medicine, though now recognized as highly toxic.