My mind started working on a weird idea (again) and I wondered. What sort of jewellery would witches and wizards wear?
In the books they seem to favour silver over gold - at least I can't remember any gold jewellery. (The ring of Slytherin, perhaps, is gold?)
I know they find goblin-wrought items valueable, but are they likely to use gemstones? Or magically made stones? I just can under no circumstances imagine someone from the old rich families, (like for example Lucius Malfoy,) giving his wife a necklace you'd risk a rich Muggle woman would wear.
That said - the sword of Gryffindor and the diadem of Ravenclaw are both items that would be found on a Muggle (at that time of history).