46. Most diamonds have been found in __C__.
A. North America B. South America C. Africa D. Arkansas
47. Diamonds in their original ground have been found __A___.
A.in Arkansas B. in several states C. around the Great Lake D. All of the above
48.The Murfreesboro field was __C__.
A. never mined B. mined until there were no more diamonds
C. not worth mining D. mined large valuable stones
49. In Murfreesboro today, the visitors can__C__.
A. watch miners at work B. explore an old mine C. hunt for diamonds D. find large valuable stone
50. The diamonds found along the Great Lakes were_D___.
A. carried there from other places B. not found in their original ground
C. found in the rocks where they were formed D. both A and B
世界上大多数的钻石来自非洲,但在美国,他们发现一个地方有砖石.那就是莫夫里斯波洛附近,阿肯色州.
首次在莫夫里斯波洛附近发现砖石是在1906,大约5万的砖石都开采自这个领域.一个40克拉（克拉）的钻石是有史以来在北美发现的最大的.但大部分的石头太小,不值得开采.很快,所有的采矿作业停止.今天一个拜访者自己访问莫夫里斯波洛去寻找钻石.
他在大湖的砂和砾石（砾石）发现了一些钻.但这些砖石不是在它们最初被开采的地方.他们可能形成于遥远的北方,最后被大冰川（冰川）运输到南方.