What is a rainbow Moldavite? One does not often come across this term. It is more of a creative name used by some sellers.
The majority of Moldavites is in all its volume homogenous in color (from light green to brown). The exception to this are bicolored Moldavites.
Bicolored Moldavites are two pieces of molten glass joined together and therefore have two different colors. They are extremely rare. More on this topic to come.
It is a regular Moldavite. Its all-over coloring is uniform. The effect of a rainbow can sometimes be seen on its damaged part.
Mining is what usually damages Moldavites. Perhaps when a Moldavite is unluckily stricken by a tool. Sometimes the Moldavite breaks into many pieces, sometimes only a small part chips off.
A Moldavite’s fracture is conchoidal and glassy. With some fractures, when the light hits the surface at just the right angle, a rainbow effect may be visible. And there you have it, a rainbow Moldavite 😉