CINNABAR [ Sulfides and Sulfosalts ]

HgS, mercury Sulfide

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.

Physical Characteristics

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

Bagikan Artikel ini