Rubellite is red tourmaline, and the tourmaline group has a stranger history than its quiet reputation suggests.
The stone in the Russian Diamond Fund long known as Caesar's Ruby, a large raspberry-red pendant carved as a bunch of grapes, is a rubellite rather than a ruby, another instance of the pre-modern habit of naming red stones by colour rather than by species.
Tourmaline's most peculiar property was noticed early by Dutch traders, who called it aschentrekker, the ash-drawer, because a heated crystal attracts ash and light debris. That is pyroelectricity: a change in temperature alters the charge distribution across the crystal, which has no centre of symmetry along its principal axis. Tourmaline is also piezoelectric, generating a charge under pressure, and this was put to practical use in the twentieth century in pressure gauges.
The stone's largest single market was not European. In the late nineteenth century pink and red tourmaline from the mines of San Diego County in California was shipped in quantity to China, where the Qing court under the Empress Dowager Cixi bought it for carving and for burial goods. The trade was substantial enough that the collapse of the Qing in 1911 took the California tourmaline industry down with it.
Chemically the tourmalines are a group rather than a species, a family of borosilicates in which many elements can substitute, which is why they occur in a wider range of colours than almost any other gem material, and why a single crystal can be zoned through several of them.