spinel ruby

Such red spinels should be called "Ruby spinel" (and not spinel ruby).

Not only is Spinel ruby related to corundum ruby in color and use, but the two are frequently associated together in nature.

The Spinel ruby of the French crown jewels, weighing 56 carats, was in 1791 valued at ten thousand dollars.

A ring with a spinel ruby in it dropped out: she recognised the stone—it was Miss Minerva's ring.