Rubellite is a red-colored gemstone differing from rubies in several ways: it is more rare than ruby; it is less dense; it is not as fiery or brilliant; and it is not as hard as a ruby. The beautiful red color of rubellite makes it desirable for jewelry, like ruby, but it is actually a tourmaline. Because it is less desirable for most buyers, rubellite is also much less expensive.
Rubellite has been mistaken for actual rubies for centuries because to the eye they look identical. It is only with the development of modern testing technique that a scientific approach for distinguishing between them has become possible.
Ruby rates a 9 on the Mohs scale, which measures hardness of gemstones. A rubellite measures a 7.5 on that scale. Ruby measures between 3.90 to 4.10 in relative density while Rubellite measures only between 3.03 to 3.10.
One characteristic of rubellite is that it is pyroelectric. This means when the gem is heated, it becomes electrically charged. Rubellite also has pleochroism, which means that it appears to be different colors when looked at from different angles. Another red gem that is often mistaken for ruby is the red spinel, which is often mined alongside rubies.