Primary ore of mercury, a pigment and as a minerals specimen
Cinnabar is a colourful mineral that adds a unique colour to the mineral colour palette. Its cinnamon to scarlet red colour can be very attractive. Well shaped crystals are uncommon and the twinned crystals are considered classics among collectors. The twinning in cinnabar is distinctive and forms a penetration twin that is ridged with six ridges surrounding the point of a pryamid. It could be thought of as two scalahedral crystals grown together with one crystal going the opposite way of the other crystal. Cinnabar was mined by the Roman Empire for its mercury content and it has been the main ore of mercury throughout the centuries. Some mines used by the Romans are still being mined today. Cinnabar shares the same symmetry class with quartz but the two form different crystal habits.
Colour : bright scarlet or cinnamon red to a brick red
Luster : adamantine to submetallic in darker specimens
Transparency : crystals are translucent to transparent
Crystal System : trigonal; 32
Crystal Habits : individual, well formed, large crystals are scarce; crusts and crystal complexes are more common; may be massive, or in capilary needles. Crystals that are found tend to be the six sided trigonal scalahedrons that appear to have opposing three sided pyramids. It also forms modified rhombohedrons, prismatic and twinned crystals as discribed above.
Cleavage : perfect in three directions, forming prisms
Fracture : uneven to splintery
Hardness : 2 – 2.5
Specific Gravity : approx. 8.1+ (very heavy for a non-metallic mineral)
Streak : red
Other : silghtly sectile and crystals can be striated
Associated Minerals : realgar, pyrite, dolomite, quartz, stibnite and mercury
Major Occurrences : include Almaden, Spain; Idria, Serbia; Hunan Prov., China and California, Oregon, Texas, and Arkansas, USA
Best Indicators : crystal habit, density, cleavage, softness and colour