Period 6 element between barium and hafnium, and radium and rutherfordium, respectively. This convention is entirely a matter of aesthetics and formatting practicality; a rarely used wide-formatted periodic table inserts the lanthanide and actinide series in their proper places, as parts of the table's sixth and seventh rows (periods). Lanthanum is a chemical element with the symbol La and atomic number 57. It is the first element in the lanthanide series. It is a soft, ductile, silvery-white metal that tarnishes rapidly when exposed to air and is soft enough to be cut with a knife. It is the eponym of the lanthanide series,
Calamine brass Calamine brass Calamine brass is brass produced by a particular alloying technique using the zinc ore calamine directly, rather than first refining it to metallic zinc. Direct zinc smelting appears to have been unknown in Europe until the mid-18th century, even though the alloyed calamine brass was in use for centuries, and metallic zinc was produced directly via reducing-atmosphere smelting in India and China from the 12th century CE onwards. Brass is an alloy of copper and zinc and, when it was first developed, methods for producing metallic zinc were unknown. Metallurgists wishing to produce brass thus used calamine (actually