Minerals occur in following forms: 1. In igneous and metamorphic rocks, minerals occur in the veins and the lodes.For instance, tin, copper, zinc and lead etc. are obtained from these veins and lodes. 2. In sedimentary rocks minerals occur in beds or layers. They have been formed as a result of deposition, accumulation and concentration in horizontal strata.Coal and some forms of iron ore are found in it. Other groups of Sedimentary minerals such as gypsum, potash salt and sodium salt are formed with the help of evaporation especially in dry regions. 3. Another mode of formation involves the decomposition of surface rocks, and the removal of soluble constituents, leaving a residual mass of weathered material containing ores. Bauxite is formed in this way. 4. Some minerals occur as alluvial deposits in sands of valley floors and base of hills. These deposits contain minerals which are not eroded by water. For example, gold, silver, tin and platinum. 5. Ocean waters contain vast quantities of minerals. Common salts, magnesium and bromine are derived from ocean waters. The ocean beds, too, are rich in manganese nodules.