Formed in the lithospheric mantle under conditions of extreme heat and pressure, lumps of metastable allotropes of carbon – better known as diamonds – have fueled wonder and greed in civilization since the days of ancient India. Found in deposits near the surface, by the 4th Century BC several Indian settlements were trading in diamonds, which inevitably found their way to Europe. Although uncut and unpolished – the technology for this wouldn’t be developed until the late 1300s – diamonds became a marker of power and privilege. They still are, although now faux diamonds can be made in labs.