When people first see these agates that strut their highly polished surfaces, everyone assumes that they have been coated with varnish. That is not the case. These incredible agates became free from their basaltic matrix and ended up in the rivers of southeastern Brazil. In the sands of some of the rivers, including the Jequitinhonha River located in Minas Gerais, Brazil, there is diamond dust as well as diamonds. In fact, diamonds have been mined in Brazil since 1725. Over thousands of years, the river agates became naturally polished by the diamond dust resident in the sands of the rivers.
Agates mostly occur as nodules in volcanic rocks or waters containing Silica in solution which is possibly derived from the decomposition of Silicates in the lava. The Siliceous matter is deposited in regular layers resulting in the banded or striped formation. It is very unlikely that you would ever find an exact duplicate of any type of Agate, Fairburn or other.