Gold dore is a bar or "button" of semi-purified gold (e.g. bullion). After we process our raw material to collect the placer gold values, some of the "fine" (A.K.A. "flour") gold is smelted in a Vcella Model L pot furnace using a crucible made of graphite along with a "flux" (a mix of Borax, silica sand, soda ash and sodium nitrate) that floats on top of the metal and absorbs most of the non-gold impurities. Once the gold and impurities are molten it is poured into a mold and cooled. After the smelted product has cooled the impurites form into a glass-like substance that can be chipped away from the gold dore. It is then remelted and poured into another mold or cuppola to produce a cast bar or "button" (gold dore). The resulting gold dore bar or button is nearly pure gold along with minor amounts of other metals like silver, platinum, palladium, etc..
It takes one more step to produce .995-.999 "pure" gold bullion. The next step would be soaking the gold dore in nitric acid to disolve the silver and platinum group metals. Gold is the only metal not affected by nitric acid.