Rubies and sapphires are varieties of corundum (aluminium oxide). In its purest form corundum is colourless. However, during formation local impurities create a range of different colours. Rubies are coloured by chromium and are always red. Sapphire is coloured blue by iron and titanium, though other colours result from different combinations and proportions of impurities. When this occurs, the name sapphire should be prefixed with the colour. When ‘star’ rubies or sapphires are viewed under directional lighting, a six-pointed ‘star’ can be seen to glide over their surface. These gems are filled with many fine, needle-like inclusions, aligned in three directions. Light is reflected from the inclusions to create three intersecting bright rays, an effect known as asterism.
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.