“Rainbow diamonds” is a commercial name used for synthetic rutile (or titanium dioxide), a diamond stimulant introduced in 1948 and popularized for some of its gemmological properties, which were close to those of natural diamonds. Synthetic rutile has a high refractive index dispersion; both of which are higher than those of diamonds. These features make rainbow diamonds look more brilliant when cut. In fact, synthetic rutile’s colors appear opal-like in the iridescence.
Synthetic rutile has long since been marketed with beautiful names - like “rainbow diamonds.” These names insinuated its superiority to natural diamond in terms of brilliance and other aspects, to an extent of demanding higher prices per carat.
However, the popularity of rainbow diamonds has declined for various reasons.
For one, the main use of rainbow diamonds was for mounting, like a ring stone, but synthetic rutile isn’t well-adapted for this purpose.
It is brittle and soft , with a low hardness of 6 on the Moh’s Scale of Hardness. In this case, it is not as durable to withstand the wear exposed to ring stones.
It also has an indisputable yellow tint that was hard for producers to remedy – and seems to be a drawback for diamond enthusiasts.
How Are Rainbow Diamonds Made?
We mentioned that synthetic rutile was used as early as 1948 as the stimulant to produce what was then marketed as rainbow diamonds. There is always debate around whether this substance is added to real diamonds, or gemstones, or diamond alternatives. For this reason, it is almost impossible to say whether a rainbow diamond from “back then” or present day is worth more (or less) than a straight-forward diamond.
Synthetic rutile can be produced synthetically by either the Czochralski method or flame fusion method. Because of rutile's high refractive index, it was used as an early diamond simulant. However, it is rarely used today as such because of its low hardness. Synthetic gems have the same chemical, optical, and physical properties of their natural counterparts, but are a more cost-effective alternative to a natural gem.
Bear in mind, however, that depending on certain ring settings and diamond arrangement, real diamonds can sometimes reflect and refract rainbow colours. This shouldn’t be confused with the synthetic rainbow diamond.
To have you own unique diamond or gemstone pieces commissioned, get in touch with a Jenna Clifford consultant today to schedule your one-on-one consultation!