Quartz is one of the most common minerals in the Earth's crust. The beauty of much quartz derives from other minerals trapped or grown within it. The coloured spangles seen in aventurine quartz are caused by small reflecting flakes of green fuschite mica, brown iron oxides or silvery coloured pyrite crystals. When quartz forms as a mass of microscopically small crystals it is known as ‘microcrystalline quartz’ or ‘cryptocrystalline quartz’. This family includes all varieties of chalcedony such as agate, carnelian and sard. Opaque, granular microcrystalline quartz is known as jasper. Chalcedonies and jaspers occur in a huge variety of colours, created by small amounts of impurities such as iron, manganese and chrome.
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.