Gold ore
Gold is found in gold ore or mixed in rocks and sand. Gold ore is often found with quartz or silica minerals. Gold is also found in alluvial deposits, or washed into streams and rivers.
Gold ore is generally divided into two main types: gold ore and gold metal ore. Gold ore is ore in which gold has reached a purity of 75-95%. This type of ore is melted from deep within the earth and pushed up by the movement of the Earth's crust. Gold has a yellow color and appears as gold dust or granules.
Huge gold deposits appeared during the Earth's formation when molten iron sank to the Earth's core, carrying with it vast quantities of precious metals.
Gold ore in Vietnam is usually polymetallic ore. The gold, not yet melted, is mixed with other metals such as copper, iron, and silver. To extract this type of gold ore, various gold processing methods must be used, depending on the properties of each gold-contaminated ore.
It is estimated that there are approximately 250,000 tons of gold in the world . To date, only about 150,000 tons have been mined. The largest gold deposit in the world was found in the Moliagul region of Victoria, Australia, in 1869 by John Deason and Richard Oates.
Although the exact time is unknown, it is estimated that gold ore was first discovered approximately 5,000 years ago. The first gold deposits were mined in Egypt in the first or second century AD. Existing Egyptian paintings show that gold mining involved several stages. Gold was panned in water, with the lighter sand floating to the surface while the heavier gold particles sank to the bottom. From 3000 BC, gold rings were used as a form of exchange. Besides being used for coins, gold was often used in decorative objects. Around 2000 BC, the Greeks and Romans knew how to extract gold from ores deep underground.
In Vietnam, the 14th century is considered the heyday of gold mining in Bong Mieu. Mining continued into the 15th century and flourished under the Nguyen dynasty... However, for the world to know and admire the reputation of "Bong Mieu gold," the years of French exploitation at this mine must be mentioned.
It was during the period from 1890 to 1895 that the French "resolved" to occupy and organize the construction of the Tam Ky - Bong Mieu road, and at the same time established a company specializing in gold mining called the Bong Mieu Gold Company. By 1939, the French had extracted 2,283 kg of gold from the Bong Mieu gold mine.
After the war ended, the Bong Mieu gold mine was devastated and ruined by bombs and bullets. Following the complete liberation of South Vietnam, the Bong Mieu gold mine continued to be illegally exploited by local people. The peak of this "gold hunt" was in the 1970s, 80s, and 90s.
On April 6, 2006, the Bong Mieu Gold Mining Company (a joint venture between Olympus Pacific Minerals Inc. (registered in Canada), the Mineral Development Company (Ministry of Industry), and Quang Nam Mineral Industry Joint Stock Company) officially commenced operations after nearly 15 years of exploration and preparation. The company's total investment was $40 million, with foreign investors holding 85%.
In 1993, the geological team of the Central Vietnam Geological Federation assessed Phuoc Son as having very high gold reserves, making Quang Nam the area with the largest gold reserves in the country. Geological exploration estimates in Phuoc Thanh commune were over 14 tons, Phuoc Kim 7 tons, and Phuoc Hiep 9 tons. In Phuoc Duc, where the Phuoc Son Gold Company mine is currently operating, the gold reserves are not disclosed but are considered one of the best gold mines in Asia. In addition, 13 other locations scattered throughout Quang Nam province also have fairly high gold reserves, spread over 10,000 km2. Prior to that, in 1980, the Vietnam Institute of Geology and Mineral Resources explored and assessed estimated reserves of over 35 tons. According to this document, the Bong Mieu gold mine had a gold content of 3-5 grams per ton of ore, but Phuoc Son had up to 13 grams of gold per ton of ore.
Windmills
A windmill is a small structure designed to convert wind power into energy to rotate blades, thereby grinding or milling grains. Modern windmills are also used to generate electricity or power water pumps (for irrigation or drainage).
It is believed that Emperor Hammurabi of Babylon planned to use windmills to power his ambitious irrigation project as early as the 17th century BC.
Windmills were used in Persia (modern-day Iran) as early as 200 BC. Heron's windmill in Alexandria marks one of the earliest known instances of a wind-powered machine in history. The Greek engineer Heron, from the 1st century AD, knew how to use windmills to power a machine. In Tibet and some other parts of China, windmills had been in operation since the 4th century. However, the windmill is more widely known to have been built in Sistan, a region between Afghanistan and Iran, from the 7th century. The windmill bodies were vertical shafts, and had rectangular blades.
During the Middle Ages, people used windmills to grind flour. They had to constantly monitor the wind. When the wind was weak, they had to use a pole to adjust the position of the windmill blades.
When the wind was too strong, adjustments had to be made to prevent the windmill from burning out. By the 12th century in Europe, windmills had undergone many improvements to adapt to unpredictable wind patterns. In the 17th century, the Dutch utilized windmills to pump water for land reclamation purposes, expanding their territory.
The earliest windmills used blades that rotated in a horizontal plane around a vertical axis. These windmills were documented by the Polish geographer Estakhri as being present in eastern Persia in the 9th century. In ancient times, the blades consisted of 6 to 12 pieces covered with reeds or cloth and used for grinding grain or pumping water. These differed from later European windmills in the 18th and 19th centuries in that the blades were mounted vertically on a horizontal axis. Windmills were widely used throughout the Middle East and Central Asia, and later spread to China and India. A windmill found in China dates back to the Jurchen Jin dynasty (1115–1234).
In Europe, a windmill used for grinding grain was discovered around 1185 in the village of Weedley in North Yorkshire (England). By the end of the 13th century, many windmills had been improved to operate even with weak winds. Windmills subsequently became quite common in England, its colonies, Germany, and Denmark.
Later, the propellers were improved so that they were not used for grinding grain or pumping water, but for generating electricity.
Sailboat
A sailboat is a type of boat powered by wind using sails. Humans have been using sailboats since the early days of civilization. The ancient Romans were the first to attach sails to rowboats to combine both human power and wind power.
Today, sailing is used all over the world. In Western countries such as the United States, Australia, New Zealand, and European countries, sailing is a very popular sport.
In Asia, Hong Kong (China), Singapore, and Thailand also have many sailboats. In Vietnam, however, since the advent of diesel engines, the number of sailboats has been steadily decreasing.
The Mesopotamian civilization was one of the first to develop. They invented the wheel, the wedge, and the sailing ship. Sailing ships were most important to them because transportation was essential. Around 5,000 years ago, the Mesopotamians began using sailing ships. Since Mesopotamia was situated between the two famous rivers, the Euphrates and the Tigris, they needed to transport water for travel and trade. A civilization that thrives on trade, Mesopotamia was no exception. They sought to establish trade relations with neighboring cities and other countries.
These were the days before roads were built, making land-based freight transport both busy and difficult. Therefore, they had to find new methods of transportation. This led to water transport, and the first types of boats were invented.
Boats transported people and goods downstream and then upstream. Sailing ships greatly assisted the Mesopotamian people in trade. Mesopotamian sailing ships helped them establish trade relations with other cities and countries, making them one of the most famous civilizations of the time.
Around 3,500 BC, the Egyptians knew how to construct sails from papyrus or linen on their boats. Thanks to sailing ships, ancient peoples were able to travel to new lands.
Over the centuries, the Egyptians and Greeks built a vital maritime economy in the Mediterranean. Many ships with large sails ventured south into the Red Sea and the Atlantic. Major sailing expeditions advanced toward West Africa and Northern Europe, further expanding the horizons of the world known to mankind.
Source: https://daidoanket.vn/tu-bao-gio-vay-ky-17-10283235.html
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