Metals of antiquity metal. While widely known during antiquity, these metals are by no means common. Yet all were known and available in tangible quantities in ancient times. Each of the metals was associated with one of the seven then-known celestial bodies, and one of the seven days of the week. Metals of antiquity The metals of antiquity are the seven metals which humans had identified and found use for in prehistoric times: gold, silver, copper, tin, lead, iron, and mercury. These seven are the metals from which the modern world was forged; until the discovery of arsenic in the 13th century, these
Regolith-hosted rare earth element deposits Regolith-hosted rare earth element deposits Regolith-hosted rare earth element deposits (also known as ion-adsoprtion deposits) are rare-earth element (REE) ores in decomposed rocks that are formed by intense weathering of REE-rich parental rocks (e.g. granite, tuff etc.) in subtropical areas. In these areas, rocks are intensely broken and decomposed. Then, REEs infiltrate downward with rain water and they are concentrated along a deeper weathered layer beneath the ground surface. Extraction technology of the deposits has been evolving over the last 50 years. In the past, REEs were primarily extracted in small amount as by-products in mines of other metals or