Pennyweight Act of 1878; only the Troy ounce and its decimal subdivisions remained official. The Troy ounce enjoys a specific legal exemption from metrication in the UK. The pennyweight is the common weight used in the valuation and measurement of precious metals. Jewellers use the pennyweight in calculating the amount and cost of precious metals used in fabricating or casting jewellery. Similarly, dentists and dental labs still use the pennyweight as the measure of precious metals in dental crowns and inlays. Pennyweight and grains are still used to weigh gooseberries in competitions in Cheshire, northwest UK. Over the Pennines in Yorkshire
Hierarchy of precious substances Hierarchy of precious substances In popular culture, sets of precious substances may form hierarchies which express conventional perceived relative value or merit. Precious metals appear prominently in such hierarchies, but as they grow, gems and semi-precious materials may be introduced as part of the system. The sequences can provide interesting examples of the arbitrariness of semiotic signs. Jubilees have a hierarchy of years: silver (25 years), ruby (40 years), golden (50 years), diamond (60 years), and platinum (70 years). Wedding anniversaries extend the jubilee hierarchy with various sequences of substances filling in many of the gaps between the same major