Heavy minerals identification

J, J, Berzelius and his collaborator Wilheim Hisinger, isolated from a heavy mineral found in 1781 in a mine at Bastnas, Sweden, another similar and yet somewhat different "earth". This one was named ceria and the mineral cerite after the then recently discovered planetoid Ceres, It was believed at the time, that both yttria and ceria were single elements, but subsequent study showed each to be a mixture of oxides, the complete separation and identification of which required more than a century of effort. 

Density is one of the properties that may be used to separate minerals. There are many procedures for obtaining so-called heavy mineral fractions from soils. These fractions consist of minerals with densities greater than those of the more common minerals such as quartz and feldspars. In a previous section the classical use of density gradients to compare soils was mentioned. A logical further step is the precise identification of the various minerals in the different fractions, particularly the denser fractions, since these are likely to be the most diagnostic. 

Although optical examination is undoubtedly the most useful single method for heavy mineral analysis, other methods may sometimes give additional information. The most important use of these is X-ray diffraction, which can be used to identify any mineral the powder pattern of which is already known. The X-ray Powder Diffraction Data File published by the American Society for Testing Materials contains data for a large number of minerals. Many patterns for ore minerals have also been published by Berry and Thomson [1962]. Novitzky [1957] includes tables of data for microscopic identification as well as X-ray powder data for 298 opaque minerals. 

Of the various physical techniques that can be used for mineral identification, thermal methods such as weight-loss curves, differential thermal analysis, and differential thermo-gravimetric analysis are the most useful. However, as these methods are only appUcable to minerals that undergo some reaction involving a change in weight, or the evolution or absorption of heat, their use for heavy minerals is limited. A punched card system with differential thermal analysis data for minerals (Mackenzie [1962]) contains information on a number of heavy minerals. 

Spencer, C. W., 1960. Method of mounting silt-size heavy minerals for identification by liquid immersion. /. Sediment. Petrol. 30 498. 

TLC has been used for the identification of heavy metals in aquatic plants. For this purpose, plants were mineralized with cone. H2SO4, HNO3, and HjOj, extracted with water, derivatized with dithizone, and chromatographed. The identified metals were zinc, copper, mercury, and lead [31]. 

The soil and sediments represent potential accumulators of heavy metals of enormous capacity. As polluters of natural waters, heavy metals come into contact with silicate minerals, hydrous oxides, carbonates, organic substances and other potential substrates in the soil and sediments and interact with them. Identification of the substrate, as well as defining the type (i.e. the strength of the connection the heavy metals make with the substrate) is of key importance for understanding the chemical behaviour of heavy metals in these environments. 

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