This Moss Agate is beautiful! I has a section of such dense dendrites at the base that it appears almost black! Moss agate is a semi-precious gemstone, a type of chalcedony with beautiful green, brown, or black dendritic (plant-like) inclusions that look like moss or lichen. It is formed from silicon dioxide (quartz) with iron/manganese oxides; it's prized for its connection to nature, grounding, stability, and tranquility, often called the "gardener's stone" for its association with agriculture and new beginnings.