**3. Conclusions**

Genesis, uses and environmental implications of iron oxides and ores have been considered in this chapter. Natural iron oxides occur extensively and are obtained from deposit of various types. Hematite is mainly sourced from iron ore of sedimentary origin including hydrothermal, metamorphic and volcanic deposits. Mafic and ultramafic rocks are linked with magnetite. This is also associated with skarn-type metamorphic deposits.

A mixture of ferrous or ferric oxides constitutes iron oxides provided for pigments. These may contain impurities of manganese oxides, clay and silica. Oxides of iron remain one of the pigments of natural origin including titanium dioxide. They are highly valued because they possess non-toxic, inert, opaque and weather-resistant properties. Oxides of iron constitute the main component of products in the pharmaceutical industry, paint industry, plastic industry, ink industry and cosmetic industry. Oxides containing mica provide anticorrosion properties. Natural pigments which qualify for these applications are limited in occurrence. Thus, synthetic iron oxides obtainable from iron compounds have better uniformity, purity of color, consistency and strength. Beneficiation processes of iron ore generate dust in the atmosphere, acid mine drainage in the ecosystem and metallic iron for steelmaking.

The main sources of air contamination during the beneficiation processes are emission of poisonous gases such as nitrous oxide, carbon dioxide, carbon monoxide and sulfur dioxide. Beneficiation process requires dissolution of minerals surrounding the ore and the release of metals and cement matrix into courses of water. These generate acid leading to acid mine drainage. Excess acidity and metal load in the ecosystem result in the loss of ecological balance and health hazards. Therefore, there is a need for valuation of the environmental impact in the planned beneficiation cycle. Sustainable beneficiation is required to reduce its impact on the natural, social or economic environment.

Reduction of heavy metal load from sewages, before their issue to the ecosystem, is a significant problem of contemporary wastewater handling. Ochre and oxides of iron have been used to test the removal of heavy metals including copper and zinc from contaminated aqueous environment. This process is governed by solution pH, metal concentration, ochre (i.e. adsorbent) concentration and contact time of reaction.
