The fascinating factor of Geochemistry is its position which is primarily in between exact sciences such as physics, chemistry and mathematics and that of natural sciences. The shape of the quantitative approach taken in physical chemistry, thermodynamics, analytical chemistry and mathematics to natural observation opens up uncharted territories and provides enormous advantages. These are neutralized, however, by the inevitable shortcomings that have to be faced when writing a script on geochemistry: and the most important of them is the need to summarize and apply quite often in a superficial and incomplete fashion, concepts that would require an entire volume if they were to be described with sufficient completeness and accuracy.