2. 外语
  3. 1 Because a diamond is made of pure carbon, it has an immensely strong crystal structure, making it the hardest of all minerals.

1 Because a diamond is made of pure carbon, it has an immensely strong crystal structure, making it the hardest of all minerals.

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问题 1 Because a diamond is made of pure carbon, it has an immensely strong crystal structure, making it the hardest of all minerals. Evidence suggests that diamonds were formed deep within the earth, and some stones may be three billion years old. Alluvial diamonds, those recovered from river gravel, can be carried long distances in rough water with other rocks. Diamond-bearing gravel is the result of one of nature’s sorting processes. Many of the diamonds found in gravel are of gem quality because flawed or fractured stones are more likely to be broken up and eroded away.
2 A diamond shines with great luster and fire, properties that are best revealed in the cut known as "brilliant." The brilliant cut dates from the seventeenth century and remains the most popular cut today because it enhances the brilliance of the gem with the least possible sacrifice of weight. It typically has 58 facets, but sometimes up to 104, and resembles two pyramids set base to base.
3 Most natural diamonds are nearly colorless, but truly colorless diamonds are rare. A few stones are found of all colors in the spectrum, and good-quality ones are known as "fancies." Diamonds of exceptional beauty and rarity are highly prized. Some have long, recorded histories, and others have inspired fantastic legends. The deep blue Hope diamond has a reputation for bringing bad luck; however, the sinister stories about it are untrue. At more than 45 carats, the Hope is one of the world’s largest diamonds and is apparently flawless.
The passage mentions all of the following about diamonds EXCEPT their
选项 A、hardness
B、formation
C、appearance
D、price
答案D
解析 The passage does not mention the price of diamonds. All of the other answers are mentioned: ...the hardest of all minerals; ...diamonds were formed deep within the earth...; ...great luster and fire...; ... brilliance...; ... nearly colorless...; ... exceptional beauty....
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