Heavy metals are here treated as light metals and, in general, are not further considered. The heaviness of naturally occurring metals such as gold, copper, and iron may have been noticed in prehistory and, in light of their malleability, led to the first attempts to craft metal ornaments, tools, and weapons. All metals discovered from then until 1809 had relatively high densities; their heaviness was regarded as a singularly distinguishing criterion. From 1809 onwards, light metals such as sodium, potassium, and strontium were isolated. Their low densities challenged conventional wisdom and it was proposed to refer to them as "metalloids" (meaning "resembling
Permanente Metals Permanente Metals Permanente Metals Corporation (PMC) is best known for having managed the Richmond Shipyards in Richmond, California, owned by one of industrialist Henry J. Kaiser's many corporations, and also engaged in related corporate activities. These four of the seven west coast Kaiser Shipyards were known for their construction of Liberty ships. The company was also a major producer of magnesium during World War II. To make use of its major product, powdered magnesium, PMC also developed and supplied an incendiary bomb mixture of magnesium powder, asphalt, gasoline and others components (known as "goop", with similar characteristics to napalm); 17,000