Moss agate is a gemstone with a pattern of thin green filaments that look similar to creeping moss or other plants. It is also called mocha stone, a name derived from the city of Mocha in Yemen, which was a major source of moss agate in the ancient world.

Like most gemstones, moss agate has long been used for personal adornment. It was known as a lucky stone in eighteenth-century America, and some ancient cultures also believed it had healing properties. Because of its moss-like green inclusions, farmers believed it helped promote healthy crops and good harvests.