Cinnabar

Cinnabar
Cinnabar, Staatliches Museum für Naturkunde Karlsruhe, Germany
General
Category	Sulfide mineral
Formula	Mercury(II) sulfide, HgS
IMA symbol	Cin[1]
Strunz classification	2.CD.15a
Crystal system	Trigonal
Crystal class	Trapezohedral (32) (same H–M symbol)
Space group	P3121, P3221
Unit cell	a = 4.145(2) Å, c = 9.496(2) Å, Z = 3
Identification
Color	Cochineal-red, towards brownish red and lead-gray
Crystal habit	Rhombohedral to tabular; granular to massive and as incrustations
Twinning	Simple contact twins, twin plane {0001}
Cleavage	Prismatic {1010}, perfect
Fracture	Uneven to subconchoidal
Tenacity	Slightly sectile
Mohs scale hardness	2.0–2.5
Luster	Adamantine to dull
Streak	Scarlet
Diaphaneity	Transparent in thin pieces
Specific gravity	8.176
Optical properties	Uniaxial (+); very high relief
Refractive index	nω = 2.905 nε = 3.256
Birefringence	δ = 0.351
Solubility	1.04×10−25 g/100 ml water (Ksp at 25 °C = 2×10−32)[2]
References	[3][4][5][6]

Cinnabar (/ˈsɪnəˌbɑːr/; from Ancient Greek κιννάβαρι (kinnábari)),^[7] or cinnabarite (/ˌsɪnəˈbɑːraɪt/), also known as mercurblende is the bright scarlet to brick-red form of mercury(II) sulfide (HgS). It is the most common source ore for refining elemental mercury and is the historic source for the brilliant red or scarlet pigment termed vermilion and associated red mercury pigments.

Cinnabar generally occurs as a vein-filling mineral associated with volcanic activity and alkaline hot springs. The mineral resembles quartz in symmetry and it exhibits birefringence. Cinnabar has a mean refractive index near 3.2, a hardness between 2.0 and 2.5, and a specific gravity of approximately 8.1. The color and properties derive from a structure that is a hexagonal crystalline lattice belonging to the trigonal crystal system, crystals that sometimes exhibit twinning.

Cinnabar has been used for its color since antiquity in the Near East, including as a rouge-type cosmetic, in the New World since the Olmec culture, and in China since as early as the Yangshao culture, where it was used in coloring stoneware. In Roman times, cinnabar was highly valued as paint for walls, especially interiors, since it darkened when used outdoors due to exposure to sunlight.

Associated modern precautions for the use and handling of cinnabar arise from the toxicity of the mercury component, which was recognized as early as ancient Rome.