Time to get technical - is it carat, karat? Both words are pronounced in the same way, and have a common linguistic root, but have very different meanings. Confusing the two when making or buying jewellery can be an embarrassing (not to mention expensive) mistake.

It’s now internationally recognised that a carat weighs 200mg. A carat is a unit of weight, so a one-carat stone that consists of a heavier (more dense) gemstone will be smaller than one carat of a lighter gemstone, so a one carat sapphire will be smaller than a one carat diamond (diamonds are lighter).