Fundamentally, natural spring waters owe their chattels to the rock strata through which it filters. The water begins as rain or snow, is both filtered by and picks up minerals from the geological formations that it passes through. Rain or melted snow simply filters through permeable soil or rock until it is stopped underground by impervious rock, such as clay or granite. Shallow springs emerge at the junction of permeable and impermeable rocks, close to the surface. Mineral waters usually come from much deeper aquifers from which the water rises through fissures under the pressure created by superimposed layers. The very fact that the aquifer is thus sealed off above from ground water maintains purity and unchanging mineral content. This process can take years; in essence, the water matures, like a fine wine. It can take centuries for water to reach its source.
Although other minor elements are often present, minerals found in natural waters consist largely of calcium, magnesium, sodium, potassium, bicarbonate, carbonate, sulfate and chloride. One of the most common trace elements is fluoride, which as we know, is good for the teeth. Mineral content varies of spring water varies largely due to the geology of the region. Limestone, for example, will make water rich in calcium, dolomites provide magnesium, and rocks resulting from volcanic action will bestow sodium. It has been determined that lightly mineralized water is one that possesses less than 500 milligrams per liter, medium mineralization is up to 1,000 milligrams per liter, and high mineralization is anything over 1,000 milligrams per liter, but precise definitions vary from country to country.