Residual mineral deposits
Also called: Residual concentration, Enrichment · Topic: Mineral Resources of India: Distribution and Conservation · NCERT: Class 10, Ch 5 "Minerals and Energy Resources"; Class 11, Ch 5 "Geomorphic Processes"
Meaning
Residual mineral deposits form when surface rock weathers, or breaks down, in place. Rainwater washes away the soluble parts (the parts that dissolve). The useful mineral that is left behind becomes richer. This process is called residual concentration or enrichment. Bauxite and some iron and manganese ores form this way, often under laterite caps on hot, wet plateaus.
Example
The bauxite of the Amarkantak plateau in Madhya Pradesh and the plateaus of Odisha formed as residual deposits beneath laterite.
Don't confuse with
- Placer deposits: here running water moves heavy minerals and drops them in sands elsewhere. In residual deposits the ore stays where it formed, and only the waste is removed.