Rapid and operationally simple sensing of trace concentration of dissolved toxic metals, such as zinc, copper, lead etc in water is desirable for water quality control and mitigation of human health hazard. The present study reveals that a newly synthesized hybrid inorganic material (HIM) is capable of detecting toxic metals, such as zinc, copper, lead and others in water simply through pH changes. HIM is essentially a composite granular material synthesized through rapid fusion of a mixture of amorphous hydrated ferric oxide (HFO) and akermanite or calcium magnesium silicate (Ca₂MgSi₂O₇). When a water sample is rapidly passed through an HIM mini-column, effluent pH at the exit always remains alkaline (around 9.0) due to slow hydrolysis of akermanite and steady release of hydroxyl (OH-) ions and at this alkaline pH, HFO offers deprotonated sorption sites for selectively binding toxic metal cations. Commonly encountered electrolytes such as sodium, calcium, chloride show no impact on exit pH. However, presence of trace concentration of toxic metal in water shows a significant pH drop after a specific number of bed volumes. The drop in pH is characteristic of the concentration and the type of toxic metal present. Moreover, the change in the negative slope of pH curve i.e., (-dpH/dBV) provides a sharp, noticeable peak for each toxic metal where BV is bed volumes of solution fed. From a mechanistic viewpoint, high affinity of HFO sorption sites toward toxic metal cations, ability of akermanite to maintain near-constant alkaline pH for a prolonged period through slow hydrolysis and labile metal-hydroxy complex formation provide a synergy that allows semi-quantitative detection of toxic metals at concentrations well below 1 mg/L. According to the information in the open literature, rapid detection of toxic metals using pH as a surrogate parameter has not been reported previously.