Crystalline metal silicates present a well-defined family of minerals in Geology. However in industrial water processes deposits that contain both “metal ions” and “Si” are usually referred to as “metal silicate” scales. In this paper we focus on precipitates that contain both “metal ions” and “Si” (where “metal ion” is Mg or Al) in an attempt to delineate the true nature of such Mg- Al- and Si-containing precipitates formed under the severe stresses simulating geothermal-like conditions. The purpose of this work is to deliberately form precipitates in the presence of Mg2+ or Al3+ ions and soluble silica (silicic acid) and study these with a variety of analytical techniques to reveal morphology texture structure and composition. Such precipitates are better described as “magnesium (or aluminum)-containing amorphous silica”.Furthermore inhibition experiments were carried out in supersaturated solutions of different silicate - expressed as SiO2 and magnesium or aluminum concentrations at pH values from 7.0 up to 10.0. Anionic additives were found to act as stabilizing agents probably by complexing the magnesium or aluminum cations and thus preventing “magnesium/aluminum silicate” formation. Based on a plethora of experimental data a number of useful functional insights have been generated which add to building a more complete and comprehensive picture of the mechanism of “metal silicate” formation and inhibition/stabilization.