Anthracite is a very hard metamorphic version of coal which I cut and shape with lapidary tools. No two pairs are alike. I've contrasted the Anthracite with iridescent freshwater pearls or sparkling facetted stones. The back is 23k gold leafed or silver leafed. The ear wires are sterling silver, or sterling silver plated with 18k gold (vermeil), left sterling where they rest in the ear, and they clip closed in the back.
Measurements are listed in the description for individual earrings.