Earth crust, silver content

The designahon rare is rather inappropriate. The RE metals are rare compared to the alkaline earth metals, calcium, magnesium and so on, but are not especially rare in general. Cerium, the RE metal with the highest mean content in earth crust is more common than copper. Thulium, the rarest RE metal (with the exception of promethium) is more common in the earth s crust than is silver. 

Nickel is a silver-white, lustrous, hard, malleable, ductile, ferromagnetic metal that is relatively resistant to corrosion and is a fair conductor of heat and electricity. Nickel is a ubiquitous trace metal that occurs in soil, water, air, and in the biosphere. The average content in the earth s crust is about 0.008%. Nickel ore deposits are accumulations of nickel sulfide minerals (mostly pentlandite) and laterites. Nickel exists in five major forms elemental nickel and its alloys inorganic, water-soluble compounds (e.g., nickel chloride, nickel sulfate, and nickel nitrate) inorganic, water-insoluble compounds (e.g., nickel carbonate, nickel sulfide, and nickel oxide) organic, water-insoluble compounds and nickel carbonyl Ni(CO). ... 

Bismuth is a relatively rare element and ranks 64th in abundance in the earth s crust, which is estimated to contain 0.17-0.2 ppm of bismuth. This is comparable in abundance to silver and cadmium. Bismuth content increases from ultrabasic (1 X 10 %) to acid magmatic rock (1 X 10 %) and is not concentrated in the magmatic phase. Native bismuth is rarely found in nature in cobalt and silver veins, but usually occurs as the compounds, mostly sulfide (bismuthinite or bismuth glance, Bi2S3) together with complex minerals asso-... 

The Earth s crust contains an average selenium content of0.05-0.09 mgkg approximating that of cadmium and antimony and ranking above molybdenum, silver, mercury, and uranium. Higher concentrations of selenium are found in volcanic rock (up to 120 mgkg ), sandstone, uranium deposits and carbonaceous rocks (Elkin 1982, Fishbein 1983, Einbrodt and Michels 1984, Merian 1985, Jacobs etal. 1977). There are... 

Rare elements, such as silver, with a low mean content in the earth s crust are well known if two criteria are fulfilled ... 

Antimony is a rare element Its content in the earth s crust is 0.2 g/tonne and it is the 65 most abundant element The principle mineral in ores is stibnite, antimony glance, a lead-gray sulfide Sb Sj (Figure M72). It has a brilliant metallic luster and sometimes contains gold and silver. A second mineral is uUmannite NiSbS, steel gray to black. 

The average natural content of selenium in the earth s crust is 0.09 mg/kg, but it is distributed very unevenly. Selenium accompanies sulfur in nature, so it is a minor component of sulfides of copper, silver, lead and mercury. The highest concentrations of selenium are found in igneous and sedimentary rocks (in sulfide rocks at concentrations of more than 1000 mg/kg). In areas with geological sub-soil such as this, concentrations of selenium in the soil are elevated (30-300 mg/kg). Normal levels of selenium in the soil are 0.1-2.0 mg/kg dry matter. In natural waters only trace amounts of selenium occur. Concentrations of selenium in lake and river waters range from about 0.02 to 10 p,g/L Sea water contains 0.03 to 0.25 [xg/l of selenium. 

---