To a pottery collector, a “mocha mug” isn’t meant for a coffee drink. “Mocha” is a type of decorated earthenware pottery made in England and sold in America in the early 1800s. Mocha pottery, or mocha ware, is usually utilitarian; pieces were originally used in the kitchen or during meals. It has colorful decorations painted in a slip glaze made from clay thinned with water to a liquid consistency…