Tourmaline’s colors have many different causes. It’s generally agreed that traces of iron, and possibly titanium, induce green and blue colors. Manganese produces reds and pinks, and possibly yellows. Some pink and yellow tourmalines might owe their hues to color centers caused by radiation, which can be natural or laboratory-induced.

There are a number of processes used to alter the color, apparent clarity, or improve the durability of gems.

Some gemstones have synthetic counterparts that have essentially the same chemical, physical, and optical properties, but are grown by man in a laboratory.

Any gem can be imitated—sometimes by manmade materials or by natural materials chosen by man to impersonate a particular gem.