Mark (unit) Mark (unit) The Mark (from Middle High German: Marc, march, brand) is originally a medieval weight or mass unit, which supplanted the pound weight as a precious metals and coinage weight from the 11th century. The Mark is traditionally a half pound weight and was usually divided into 8 ounces or 16 Lot. The significance of the "Cologne Mark" (Kölner Mark) in the German-speaking areas corresponded to about 234 gram. Like the German systems, the French poids de marc weight system considered one "Marc" equal to half-a-pound (8 ounces). Like the pound of 12 troy ounces (373 g), the mark
Heavy metals of elements heavier than helium in the interstellar medium. When gravitational attraction causes this matter to coalesce and collapse new stars and planets are formed. The Earth's crust is made of approximately 5% of heavy metals by weight, with iron comprising 95% of this quantity. Light metals (~20%) and nonmetals (~75%) make up the other 95% of the crust. Despite their overall scarcity, heavy metals can become concentrated in economically extractable quantities as a result of mountain building, erosion, or other geological processes. Heavy metals are primarily found as lithophiles (rock-loving) or chalcophiles (ore-loving). Lithophile heavy metals are mainly f-block