The Reverend Chauncy Hare Townshend bequeathed his important collection of 154 gems to the South Kensington Museum (now the V&A) in 1869. Although the collection is not as comprehensive as that found at the Natural History Museum, it is of particular historic interest as its formation pre-dates the development of many synthetic gemstones and artificial enhancements. All the stones were mounted as rings before they came to the Museum, mainly in a series of standardised gold settings, often of the coronet or galleried type. However, several specimens are set with greater elaboration, with diamond borders surrounding the central stone. Some of these were originally in the possession of Henry Philip Hope (d.1839), a brother of the novelist and antiquary Thomas Hope (c. 1770-1831). H.P. Hope formed a famous collection of diamonds and precious stones which was largely inherited by his three nephews. His collection, which included the Hope blue diamond, now in the Smithsonian Institution, Washington, was catalogued by B. Hertz in 1839. Townshend is recorded as having made purchases from it and also seems to have remounted several of the rings, in whole or in part.

Opal is created when water containing microscopically small spheres of silica settles in cavities and veins in the Earth. Opals occur in a great variety of body colours. Those with an iridescent play of colour are known as ‘precious’, those without are termed ‘common’. Opals contain up to 10% water. This makes them particularly vulnerable to damage from dehydration and from immersion in some cleaning products. White opal has a white body colour with a rainbow iridescence. The play of light prized in precious opal is caused by the reflection and scattering of light from minute, closely packed silica spheres.