Mercury minerals

Hg deposits are distributed along the MTL (Median-Tectonic Line) in Southwest Japan and in Northeast Hokkaido (Fig. 1.184). The deposits are vein or disseminated in form. The deposits are hosted by sedimentary and igneous rocks. No K-Ar age data on the deposits are available. However, from the age of host rocks, the age of igneous activities along MTL and the studies on the movement of MTL and K-Ar ages of Au-veins associated with Hg mineralization in Northeast Hokkaido (e.g., Khonomai), it is likely that these deposits formed at middle Miocene age. However, mercury mineralization in Kitami Province (north Hokkaido) occurred at approximately the same age as the epithermal gold-silver mineralization in the same district (4.5-5.3 Ma) (Maeda, 1997). 

Maeda, H. (1997) K-Ar age of mercury mineralization and related volcanic activity in Kitami metallogenic province, Hokkaido, Japan Specimens from Asahino disseminated and Tokoro vein-type mercury deposits. Resource Geology, 47, 11-20. 

As mentioned at the end of Section 6.9.3, reviews of the crystal chemistry of mercury minerals with lower oxidation states and with oxo-centered building blocks have been published72,73 and the structural role of Hg22+ and Hg34+ groups discussed.407... 

R. Kishi, R. Doi, Y. Fukuchi, H. Satoh, T. Satoh, A. Ono, et al., Subjective symptoms and neurobehavioral performances of ex-mercury miners at an average of 18 years after the cessation of chronic exposure to mercury vapor. Environ. Res. 62 289, 1993. 

Table I. Thermodynamic Properties of Mercury Minerals and Compounds at 298.15K, Including Estimates.

Because mercury forms relatively stable hydroxo, sulfato, and chloro complexes in solution, the solubilities and relative stabilities of mercury minerals depend heavily on ambient solution compositions. Figure 4 illustrates the calculated effect of pH and total sulfate on the solubility of schuetteite. The curves take into account all complexes for which data are available in Martell and Smith (18) and precipitation of HgO they cross when changes in solution composition result in changes in dominance among complexes. Schuetteite is quite soluble relative to HgS and elemental mercury under common conditions. 

There is no known biochemical reaction in organisms that applies Hg as an essential element. Mercury is the only metal which is a liquid at ordinary temperatures. The boiling point of this metal is 357 °C. This temperature is relatively low for metals and its vapor pressure is significant even at room temperature. The threshold limit value (TLV) of elemental mercury is 0.05 mg/m- a value that is less than the equilibrium vapor pressure at ambient temperatures. However, in the mercury miners in Sicily, where the mercury occurs in shales, the miners are exposed to elemental mercury vapor, which content in the air may reach toxic levels of about 5 mg/nr Another source of exposure in mines is the mercury-containing dust. 

The natural mercury mineralization at New Almaden is apparently responsible for most of the mercury contamination in Santa Clara County. The mercury vapor above these ore deposits has been known for a number of years (4). However, the route by which the mercury entered the local water reservoirs is not known. Certainly the air movement can act as a transporter of the gaseous mercury. 

Both natural phenomena and human activity produce airborne elemental mercury plumes. The naturally occurring plumes are usually associated with mercury mineral deposits and appear to be enhanced by mining activity or the venting of geothermal steam. The man-made plumes are associated with such activities as industry, sewage treatment plants, and refuse fill areas. The dispersal pattern of airborne mercury plumes depends on local conditions of ventilation and perhaps also on local concentrations of other contaminating molecules. 

BERG If you took a mercury mineral appearing somewhere in the precambrian shield, reputed to be highly insoluble, let it stand with a clean water sample, what kind of concentrations would you expect ... 

Arsenic is sometimes found in nature in native state and is fairly easily extracted from its compounds. It is not known who was the first to produce elemental arsenic. Usually its discovery is ascribed to the alchemist Albert the Great. Paracelsus described the process of preparing metallic arsenic by the calcination of arsenic with egg-shells. According to some reports, metallic arsenic was known much earlier but it was considered to be a variety of native mercury. This is due to the fact that arsenic sulphide resembles one of mercury minerals and the extraction of arsenic from its ores is rather simple. 

Buxen, G. Bacterial methyl mercury— mineralizing activity in river sediments. Water Res. 8, 219 (1974). 

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