Sapphires and rubies are varieties of the mineral corundum, the hardest gem mineral after diamond. Small quantities of chromium in corundum cause rubies to be red. Sapphire is the name given to any other gem corundum. Varying amounts and combinations of iron, titanium and chromium cause the range of colours of sapphires, from blues to yellows, pink-oranges and greens. The name of this type of sapphire comes from the star effect caused by the reflection of light within the crystal.
This ring forms part of a collection of 154 gems bequeathed to the V&A by the Reverend Chauncy Hare Townshend, a cleric and poet. Sir A. H. Church gave additional specimens in 1913. He also compiled the first catalogue Precious Stones: A Guide to the Townshend Collection. The first edition appeared in 1883. The stones are mounted as rings, although they may not have been intended to be worn.