Zimbabwe, elements

Rubidium [7440-17-7] Rb, is an alkali metal, ie, ia Group 1 (lA) of the Periodic Table. Its chemical and physical properties generally He between those of potassium (qv) and cesium (see Cesiumand cesium compounds Potassium compounds). Rubidium is the sixteenth most prevalent element ia the earth s cmst (1). Despite its abundance, it is usually widely dispersed and not found as a principal constituent ia any mineral. Rather it is usually associated with cesium. Most mbidium is obtained from lepidoHte [1317-64-2] an ore containing 2—4% mbidium oxide [18088-11-4]. LepidoHte is found ia Zimbabwe and at Bernic Lake, Canada. 

Russia and the RepubHc of South Africa account for more than half the world s chromite ore production. Almost all of the world s known reserves of chromium are located in the southeastern region of the continent of Africa. South Africa has 84% and Zimbabwe 11% of these reserves. The United States is completely dependent on imports for all of its chromium (4). The chromite s constitution varies with the source of the ore, and this variance can be important to processing. Typical ores are from 20 to 26 wt % Cr, from 10 to 25 wt % Fe, from 5 to 15 wt % Mg, from 2 to 10 wt % Al, and between 0.5 and 5 wt % Si Other elements that may be present are Mn, Ca, Ti, Ni, and V. AH of these elements are normally reported as oxides iron is present as both Fe(II) andFe(III) (5,6). 

The first source of chromium was found in the mineral crocoite. Today it is obtained from the mineral chromite (FeCr O ), which is found in Cuba, Zimbabwe, South Africa, Turkey, Russia, and the Philippines. Chromite is an ordinary blackish substance that was ignored for many years. There are different grades and forms of chromium ores and compounds, based on the classification of use of the element. Most oxides of chromium are found mixed with other metals, such as iron, magnesium, or aluminum. 

In the early 1800s, the principal sources of nickel were in Germany and Scandinavia, Very large deposits of lateritic (oxide or silicate) nickel ore were discovered in New Caledonia in 1865. The sulfide ore deposits were discovered in Sudbury, Ontario in 1883 and, since 1905, have been the major source of the element, The most common ore is pentlandite, (FeNi Sg, which contains about 34% nickel. Pent-landite usually occurs with pyrrhotite, an iron-sulfide ore, and chalcopyrite. CuPeS2. See also Chalcopyrite Pentlandite and Pyrrhotite, The greatest known reserves of nickel are in Canada and Russia, although significant reserves also occur in Australia, Finland, the Republic of South Africa, and Zimbabwe. 

Rhodium occurs only to the extent of 10 % in the earth s crust. Fortunately, it is not eveifly distributed, but is found, alloyed with the other platinum metals, to the extent of a few ppm (several grams per tonne) in its ores. The principal locations of these ore bodies are in the Urals near Ekaterinburg (the earliest commercial source) and in the Merensky reef near Pretoria in the Republic of South Africa. The latter is the major source today. Minor sources are found in North America and Zimbabwe. Many platinum metal resources, such as that at Sudbury in Ontario, contain very little rhodium. Various other minor sources are known, and in fact the element was first isolated by Wollaston in 1804 from impure platinum of South American origin. 

Platinum is one of the rarest elements. Its abundance is estimated to be about 0.01 parts per million in Earth s crust. The world s largest supplier of platinum by far is South Africa. In 2008, that nation produced 153,000 kilograms of platinum, 77 percent of the total world production. The next largest producer was Russia, followed by Canada, Zimbabwe, and the United States. Most of the platinum in the United States comes from the Stillwater and East Boulder Mines in Montana. 

Arsenic is widely distributed in the environment. It ranks twentieth in the abundance of elements in the Earth s crust. In the environment, arsenic is mainly associated with sulfide minerals. Soils contain arsenic usually in the range of 0.5 to 35 mg/kg [98]. Arsenic levels in gold ore deposits in Zimbabwe attain 20 g/kg in soils [99]. 

Imported Inorganic Chemical Elements, Oxides and Halogen Salts in Zimbabwe,... 

Cobalt is a comparatively rare element, ranking 32nd in abundance in the Earth s crust. It is found in sulfidic copper ores of Zaire, Africa, and in pyrites from Ontario, Canada. Additional deposits of cobalt-containing ores are found in Morocco and Northern Zimbabwe. Although deposits of... 

Major element data for tonatidc and trondhjeimtic gneisses liroiQ the north marginal zone, Limpopo belt, Zimbabwe... 

Tantalum — (Gr. Tantalos, mythological character, father of Niobe), Ta at. wt. 180.94788(2) at. no. 73 m.p. 3017 °C b.p. 5458 C sp. gr. 16.4 valence 2 , 3,4 , or 5. Discovered in 1802 by Ekeberg, but many chemists thought niobium and tantalum were identical elements until Rose, in 1844, and Marignac, in 1866, showed that niobic and tantalic acids were two different acids. The early investigators only isolated the impure metal. The first relatively pure ductile tantalum was produced by von Bolton in 1903. Tantalum occurs principally in the mineral columbite-tantalite (Fe, Mn)(Nb, Ta) 0. Tantalum ores are found in Australia, Brazil, Rwanda, Zimbabwe, Congo-... 

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