Vulcanite - a combination of sulphur and India rubber - was developed in the mid-Ninteeth century largely by Charles Goodyear (the tire guy). It can be white or lots of other colors, plus it's easy to work with, so it was often used to imitate coral, tortoiseshell and jet - especially the latter, as black mourning jewelry became more popular. This necklace has multiple rods of vulcanite strung on (slightly stretched-out) elastic. You can still smell the slightly burnt-rubber smell that is the telltale sign that you're dealing with Vulcanite and not one of the other black mourning jewelry materials. It may have been worn during the first stage of mourning, where the bereaved wasn't allowed to express themselves with decoration or color other than matte black. After a certain amount of time had passed, mauve or slightly more embellishment could be added back into one's wardrobe. Queen Victoria dictated the amount of time it was appropriate to wear mourning clothes.