MERCURY
Native mercury – Hg – is a rare native element that has a number of industrial uses, both historical and current.
Native mercury, being a liquid at room temperature, does not meet the criteria required to be a mineral, constituting a mineraloid. For historical reasons, however, it is listed as a mineral species. At room temperature it is liquid and, when heated to 357°C, it volatilizes. It crystallizes only at -38.9°C, forming rhombohedral crystals at low pressures and tetragonal crystals at high pressures. Liquid mercury must be stored in a closed container, as it volatilizes over time.
Native mercury is volatile, its vapors are highly toxic to lethal! Avoid inhaling the dust from a mercury ore. After handling minerals containing mercury, wash your hands. Preferably, use disposable gloves to prevent microdroplets of mercury from the surface of the mineral from being absorbed by the skin.
1. Characteristics
Crystal system: Trigonal.
Color: White from tin to gray-white.
Habit: Drops, globules.
Cleavage: No.
Tenacity: No.
Twinning: No.
Fracture: No.
Mohs Hardness: No.
Parting: No.
Streak: No.
Lustre: Bright metallic.
Diaphaneity: Opaque.
Density (g/cm³): 13.6
2. Geology and Deposits
It occurs in hydrothermal deposits formed at low temperatures associated with hot springs. It appears as free droplets adhering to the surface of the ore or as large liquid masses in cavities within the ore, formed by the alteration of cinnabar (HgS) in the oxidation zone of sulfide ores.
It can also be found in low-temperature limestone veins. It occurs very pure, rarely with a little silver or gold. It has been recorded in a reasonable number of locations, but rarely in significant quantities.
A very important, historical deposit is the Almadén Mine in Spain, where mining has been recorded for over 2,000 years, producing a third of all the mercury produced by humanity.
3. Mineral Associations
It is associated with moschellandsbergite (Ag5Hg8 – with approximately 70% Hg) and kongsbergite, a crystal mixture of Hg and Ag with more than 40% silver.
In addition, it ocurrs with cinnabar, meta-cinnabar, calomel, terlinguite, eglestonite, mercurian silver, mercurian gold, pyrite, dolomite, barite, and quartz.