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Zinc is refined by froth flotation of the ore, roasting, and final extraction using electricity (electrowinning). Zinc is an essential trace element for humans, [8] [9] [10] animals, [11] plants [12] and for microorganisms [13] and is necessary for prenatal and postnatal development. [14]
The first and second issues (1913 and 1920) were struck in aluminum by the Frank & Co. die establishment. All subsequent issues were minted by the newly reopened Manila Mint . The third issue (1922) was also aluminum, but the fourth, fifth, and sixth issues (1925, 1927, and 1930) were in copper-nickel alloy .
National Scientists of the Philippines (1978–1998). Pasig, Philippines: Anvil Publishing, Inc. 2000. ISBN 978-9712709326. Comrade Manokski's ORBAT- Timawa.net- "Islas de los Pintados: The Visayan Islands". Archived from the original on September 27, 2011. "Top 12 Surprising Filipino Inventions You Might Want To Know"
Scholarly information about the use of gold in early Philippine history comes mostly from artifacts that have been discovered in various sites in the Philippines, and from historical accounts from the early Spanish colonial period. Archeological excavation sites include ones in Batangas, Mindoro, Luzon, Samar, Butuan and Surigao. [7]
The Rizal Archaeological Site pushed back the first known human activity in the Philippines 10 times earlier. Prior to the excavation, the oldest fossil discovered in the country was the foot bone found in 2010 in Callao Cave, Cagayan Valley. The bone was dated at least 67,000 years old. [3]
The oldest known pills were made of the zinc carbonates hydrozincite (described 1853) and smithsonite (described 1832). Calamine is a historic name for an ore of zinc (hemimorphite (IMA1962 s.p.) and smithsonite). [6] De architectura (about 15 BC) of Marcus Vitruvius Pollio, Libri X, vol. VII, Caput 8.
The first official census in the Philippines was carried out in 1878. The colony's population as of December 31, 1877, was recorded at 5,567,685 persons. [294] This was followed by the 1887 census that yielded a count of 6,984,727, [295] while that of 1898 yielded 7,832,719 inhabitants. [296]
The earliest date suggested for direct Chinese contact with the Philippines was 982. At the time, merchants from " Ma-i " (now thought to be either Bay, Laguna on the shores of Laguna de Bay , [ 33 ] or a site called "Mait" in Mindoro [ 34 ] [ 35 ] ) brought their wares to Guangzhou and Quanzhou .