Mercury

Chemical formula: Hg

Native mercury is the only mineral that is a liquid metal at room temperature, occurring as silvery, mobile droplets.

## Characteristics Native mercury is a chemical element and a mineral from the native elements group. Its most unusual feature is its liquid state at standard temperature and pressure. It occurs as small, silvery-white, metallic droplets dispersed in the host rock. At lower temperatures (below -38.8°C), it crystallizes, forming metallic crystals with a rhombohedral structure, similar to cinnabar crystals. ## Physical Properties As a liquid, mercury does not possess hardness on the Mohs scale. It has very high surface tension, causing it to form spherical droplets. It is extremely dense, about 13.5 times denser than water. It is characterized by a strong, metallic luster. It is opaque. In its solid state (frozen), it is a malleable and ductile metal. ## Colors and Varieties Native mercury has a characteristic, silvery-white color with a slight bluish tint. It does not form color varieties. Amalgams, which are its natural alloys with other metals (mainly silver and gold), are sometimes considered its varieties, although formally they are classified as distinct minerals. ## History and Name Mercury has been known since antiquity. Its name in many languages (including English *mercury*) comes from the Roman god Mercury, patron of trade and messengers, which refers to its mobility. The chemical symbol Hg comes from the Greek word *hydrargyrum*, meaning "liquid silver" (from *hydor* - water and *argyros* - silver). Due to its toxicity, its extraction and use have been significantly restricted. ## Uses Historically, mercury was a primary source for mirror production, in thermometers, barometers, mercury lamps, and in the amalgamation process for recovering gold and silver from ores. Currently, its use is severely limited due to environmental and health concerns. For collectors, it is mainly a curiosity due to its unique state of matter.

Properties

Luster: Metallic
Streak: Tin-white
Density: 13.59
Cleavage: None
Transparency: Opaque
Crystal system: Trigonal

Diagnostic features

## Identification Native mercury is absolutely unique and impossible to confuse with any other mineral at room temperature. Its liquid state, silvery-white metallic color, and very high density are unequivocally identifying features. ## Distinguishing from Similar Minerals There are no minerals that could be confused with liquid native mercury. In its frozen state, its crystals may resemble other native metals, but upon warming to room temperature, it immediately melts, which is a diagnostic feature. ## Crystal Forms In natural conditions, mercury crystallizes extremely rarely, only in arctic climates or at high altitudes. It then forms trigonal (rhombohedral) crystals, often distorted or in the form of coatings. Most commonly, it is found as liquid droplets and globules.

Geological environment

## Genesis Native mercury forms as a result of low-temperature hydrothermal processes. It is a product of the oxidation of mercury sulfide - cinnabar (HgS), which is the main ore mineral of mercury. It occurs in sedimentary rocks (limestones, dolomites, shales) and volcanic rocks, often near hot springs and fumaroles. ## Mineral Associations It most commonly co-occurs with cinnabar, from which it directly forms. It is also accompanied by calcite, dolomite, quartz, chalcedony, barite, pyrite, marcasite, as well as other, rarer mercury minerals such as calomel and eglestonite. In some deposits, it occurs together with native gold and native silver. ## Localities The most important historical and contemporary localities include Almadén in Spain (the largest deposits in the world), Idrija in Slovenia, Monte Amiata in Italy, as well as deposits in the Kuskokwim region of Alaska (USA), New Almaden and New Idria in California (USA), Terlingua in Texas (USA), and in Guizhou Province in China.

Rarity

Not very common

For collectors

## Quality Criteria The collector's appeal of a native mercury specimen depends on the quantity and size of visible, liquid droplets against the host rock. The most prized specimens are those with numerous, large droplets (several millimeters in diameter) clearly embedded in quartz or calcite druses, often accompanied by red cinnabar, which creates an attractive contrast. Due to toxicity, specimens must be safely enclosed in a sealed container. ## Popular Localities Classic and most desirable specimens come from historical mines in the USA, such as mines in San Benito County, California (e.g., New Idria) and Brewster County, Texas (Terlingua). Specimens from these localities, often with cinnabar, are considered the standard for this mineral.

Care and storage

## Cleaning Native mercury as such does not require cleaning. Specimens of rocks with visible mercury droplets must be handled with extreme caution. They should not be touched with bare hands. All manipulations should be carried out over a tray to prevent the dispersal of toxic droplets. ## What to Avoid Avoid heating the specimen, as mercury vapors are extremely toxic. Avoid contact with skin, eyes, and respiratory tract. Do not store in poorly ventilated areas. Keep away from aluminum, with which it forms an amalgam, and from gold and silver. Do not allow contact with children and pets. ## Storage Specimens containing native mercury must be stored in sealed, unbreakable containers, preferably made of transparent plastic (e.g., perky boxes), to prevent evaporation and accidental spillage. The container should be clearly labeled as toxic. Store in a cool, well-ventilated, and secure place, inaccessible to unauthorized persons.

Sources

IMA Mineral List (CNMNC)