Group 12 element by mass, and even the leanest concentrated deposits are at least 0.1% mercury (12,000 times average crustal abundance). It is found either as a native metal (rare) or in cinnabar (HgS), corderoite, livingstonite and other minerals, with cinnabar being the most common ore. While mercury and zinc minerals are found in large enough quantities to be mined, cadmium is too similar to zinc and therefore is always present in small quantities in zinc ores from where it is recovered. Identified world zinc resources total about 1.9 billion tonnes. Large deposits are in Australia, Canada and the United States with the
Ore dock ore, in raw or taconite form. Ore docks are typically long, high structures, with a railway track or tracks along the top and a number of "pockets" into which ore is unloaded from railcars, typically by gravity. Each pocket has a chute that can be lowered to discharge the ore into the hold of a ship berthed alongside. The use of pockets and chutes allows the dock itself to be loaded with ore before it is transferred into the freighter. The docks' storage bins or pockets typically are wider at the top than the bottom, and they lead to movable