ALL standard glass has a natural green tint. The thicker the glass the darker the tint. As a general view, you can see the green tint more clearly from the edge because you are looking through a greater thickness of glass.
Low iron glass is manufactured with lower iron content which produces much clearer glass than standard ‘clear’ glass. Often the use of this extra clear glass is used in structural glazing where thicker glass or layered glass is required. If standard ‘clear’ glass was used in these thick, multi-layered structural glass installation the result would be that it would have a noticeable green tint. When using low iron glass, a thick unit of glass can be used to assemble the structural glass unit creating a clear and frameless glass installation.
The green tint is caused by an iron content with the glass, which is an impurity in the sand used to make the glass. In the glass, iron ions absorb in the red (and infra-red) and blue (and ultra-violet) parts of the spectrum, making the glass look green due to the light that is left.