Humans have used jewellery for a number of different reasons:    Most cultures at some point have had a practice of keeping large amounts of wealth stored in the form of jewellery. Numerous cultures store wedding dowries in the form of jewellery or make jewellery as a means to store or display coins. Alternatively, jewellery has been used as a currency or trade good; an example being the use of slave beads. Many items of jewellery, such as brooches and buckles, originated as purely functional items, but evolved into decorative items as their functional requirement diminished. Jewellery can symbolise group membership (as in the case, of the Christian crucifix or the Jewish Star of David) or status (as in the case of chains of office, or the Western practice of married people wearing wedding rings). Wearing of amulets and devotional medals to provide protection or to ward off evil is common in some cultures. These may take the form of symbols (such as the ankh), stones, plants, animals, body parts (such as the Khamsa), or glyphs (such as stylised versions of the Throne Verse in Islamic art). In creating jewellery, gemstones, coins, or other precious items are often used, and they are typically set into precious metals. Platinum alloys range from 900 (90% pure) to 950 (95.0% pure). The silver used in jewellery is usually sterling silver, or 92.5% fine silver. In costume jewellery, stainless steel findings are sometimes used. Other commonly used materials include glass, such as fused-glass or enamel; wood, often carved or turned; shells and other natural animal substances such as bone and ivory; natural clay; polymer clay; Hemp and other twines have been used as well to create jewellery that has more of a natural feel. However, any inclusion of lead or lead solder will give a British Assay office (the body which gives U.K. jewellery its stamp of approval, the Hallmark) the right to destroy the piece, however it is very rare for the assay office to do so. Beads are frequently used in jewellery. These may be made of glass, gemstones, metal, wood, shells, clay and polymer clay. Beaded jewellery commonly encompasses necklaces, bracelets, earrings, belts and rings. Beads may be large or small; the smallest type of beads used are known as seed beads, these are the beads used for the "woven" style of beaded jewellery.