Mercury (element) long periods at elevated temperatures. It reverts to the elements upon heating near 400 °C, as was demonstrated by Joseph Priestley in an early synthesis of pure oxygen. Hydroxides of mercury are poorly characterized, as they are for its neighbors gold and silver. Being a soft metal, mercury forms very stable derivatives with the heavier chalcogens. Preeminent is mercury(II) sulfide, HgS, which occurs in nature as the ore cinnabar and is the brilliant pigment vermillion. Like ZnS, HgS crystallizes in two forms, the reddish cubic form and the black zinc blende form. The latter sometimes occurs naturally as metacinnabar. Mercury(II)
Ore dock built in 1865. By 1884, locomotives played a vital part in hauling ore from the mines to the docks. The pockets and chutes were filled using the hopper type ore cars. In 1889, the Duluth, South Shore and Atlantic Railway operated a dock with 284 pockets. The railroads also provided alternate transportation for people, goods and eventually, iron ore. The length and capacity of docks corresponded with the capacity of the ore freighters which they were designed to accommodate. As ore carriers increased in height and width, higher pocket openings were required and it was necessary to construct new docks