One of the most attractive features of Montana agate is the colored inclusions, which are made up of minerals (such as iron and manganese). The finest Montana agate has a clear matrix with well-defined orange-red and black inclusions that form bands, specks, or other shapes. This cabochon is highly polished, round, and 38mm in diameter. Thickness, 5mm. Backside is flat and smooth.
Montana agate and sapphire are the two State gemstones of the State of Montana. Montana agate is sometimes also referred to as “moss agate” (agate that has colored inclusions that may resemble moss). Agate is a moderately hard rock, primarily composed of silica (quartz). The hardness is important for jewelry-making because relatively hard rock can take a good polish. The background of Montana agates ranges from nearly clear, through milky grey-blue to white. Montana agates were formed as the result of volcanic activity in the Yellowstone Park area millions of years ago.