Why Does Clear Glass Have a Greenish Tint?

I remember, as a kid, looking through the polished edge of a thick piece of glass. You could see this cool prism and the inside of this mysterious prism world appeared to have a greenish tint.

Later, I discovered that the glass industry calls it "Coke Bottle Green," due to the greenish hue found in many of the antique Coca-Cola bottles. The color comes from the iron minerals used in the manufacturing of glass to add strength.

The color will be darker on thicker or larger glass table tops and mirrors. This color is standard to the industry and used by most glass companies and furniture companies.

However, glass products with low-iron levels are produced for a brighter or white glass appearance. This product in the glass industry is called "Starphire" glass.