Textbook in PDF format Deep-sea mining is currently in a critical phase wherein, detailed resource estimation has led to identification of potentially rich areas on the seafloor that can be mined, as well as testing of pre-prototype seabed mining machines and establishment of pilot plants for processing of deep-sea minerals is underway. This coupled with rigorous environmental data collection along with impact assessment of simulated as well as test mining is not only providing requisite information for likely impacts for development of predictive models but also for developing mitigation measures to minimise such impacts