<Tr> <Th> Material </Th> <Td> Gold, silver, platinum </Td> </Tr> <Tr> <Th> Cap </Th> <Td> Velvet trimmed with ermine </Td> </Tr> <Tr> <Th> Notable stones </Th> <Td> Cullinan II, St Edward's Sapphire, Black Prince's Ruby, Stuart Sapphire </Td> </Tr> <P> The Imperial State Crown is one of the Crown Jewels of the United Kingdom and symbolises the sovereignty of the monarch . </P>

When does the queen wear the crown jewels