Moss Agate is a semi-precious stone composed of silicon dioxide, and is actually a form of chalcedony; it doesn't have the typical banding which is found in other agates. It contains trace minerals in different shades of green that give the stone the appearance of being mossy, some pieces appear as if you are looking into a glass terrarium. Despite the name it does not contain organic material; it is usually formed from weathered volcanic rock. This stone can be found in Australia, India, Russia, and the US and is said to help with mental function by improving concentration and awareness, relieving depression, aiding in immune function.