Toxicological trivia from July 29, 2016: Mercury is a chemical element with symbol Hg and atomic number 80. It is commonly known as quicksilver and was formerly named hydrargyrum.Mercury is an extremely rare element in Earth’s crust, having an average crustal abundance by mass of only 0.08 parts per million (ppm). Because it does not blend geochemically with those elements that constitute the majority of the crustal mass, mercury ores can be extraordinarily concentrated considering the element’s abundance in ordinary rock. It is found either as:a) A native metal (rare) or in cinnabar, corderoite, livingstonite and other minerals, with cinnabar (HgS) being the most common ore.b) Mercury ores usually occur in very young orogenic belts where rocks of high density are forced to the crust of Earth, often in hot springs or other volcanic regions; c)  Both previous assertions are correct.

Correct answer: c.  Read more in WP.