2. Measure the specific gravity. First, measure the weight of a pure gold bar with a balance, then put the gold bar into a measuring cup and pour water to drown it. Then put the detected gold bars into a measuring cup and observe whether the scale of water rises or falls. As long as there is a change, it means that gold bars are not pure gold. But if it is gold jewelry, this method is not applicable, because there is air in gold jewelry.
Real gold is not afraid of fire. Put gold bars or gold jewelry on the fire for a period of time and observe its changes. Because iridium will combine with oxygen in the air to produce oxidation reaction, gold bars with insufficient purity will turn gray; And pure gold will appear bright red after being baked by fire. However, this method may have some damage to jewelry.
Extended information (1) Gold stock on the earth: There are about137,400 tons of gold in the world, and the gold stock on the ground is still growing at a rate of about 2% every year.
(2) Annual supply and demand: The annual supply and demand of gold is about 4,200 tons, and the newly produced gold accounts for 62% of the annual supply.
(3) New gold mining cost: The average total gold mining cost is slightly lower than $260/oz. Due to the development of mining technology, the cost of gold development has been declining in the past 20 years.
(4) Political, military and economic changes in gold-producing countries: Any political and military turmoil in these countries will undoubtedly directly affect the country's gold production, and then affect the world's gold supply.
(5) The central bank sells gold: The central bank is the largest gold holder in the world. 1969 The official gold reserve was 36,458 tons, accounting for 42.6% of the total surface gold stock at that time. By 1998, the official gold reserve is about 34,000 tons, accounting for 24. 1% of the total mined gold stock. According to the production capacity, this is equivalent to 13 years of world gold minerals.
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