In the days before photography and when the vast majority of the population could not afford to have their portrait painted, there were limited ways to remember loved ones who’d passed on. The memento mori tradition most likely began with mourning rings, small bands that may have had the name of the deceased engraved inside. They quickly became more intricate.
Another fashionable remembrance involved the dead’s hair. Lengths of their hair was plaited or sculpted into a design and put under glass. This could be worn as a locket, a brooch or a ring.
Mourning jewelry, including the use of jet, a very black and workable stone, rose to popularity after Prince Albert died and Queen Victoria remained in mourning for him.
As an interesting side note, Victoria’s style quickly became the nation’s style and the area of Whitby had a boom economy as the source of most jet (fossilized wood). When she came out of mourning (sort of) two decades later the demand for jet collapsed.