首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
Diamonds are just carbon in its most concentrated form, the element that makes up 18 percent of the weight of your body. There i
Diamonds are just carbon in its most concentrated form, the element that makes up 18 percent of the weight of your body. There i
admin
2010-08-04
41
问题
Diamonds are just carbon in its most concentrated form, the element that makes up 18 percent of the weight of your body. There is no other gemstone as cherished as the diamond, but in truth, diamonds are no rarer than many other precious gems. They continue to demand higher market prices because the majority of the diamond market is controlled by a single entity.
The Origin of Diamonds
Carbon is one of the most common elements in the world, and is one of the four essentials for the existence of life. Humans are more than 18-percent carbon. When occurring in nature, carbon exists in three basic forms, of which diamond is an extremely hard, clear crystal.
Diamonds form about 161 km below the Earth’s surface, in the molten rock of the Earth’s mantle, which provides the right amounts of pressure and heat to transform carbon into a diamond. In order for a diamond to be created, carbon must be placed under at least 435,113 pounds per square inch (psi) of pressure at a temperature of at least 400 Celsius. If conditions drop below either of these two points, graphite will be created. At depths of 150 km or more, pressure builds to about 725,189 psi and heat can exceed 1,200 C.
Kimberlite Pipes
Most diamonds that we see today were formed millions (if not billions) of years ago. Powerful magma eruptions brought the diamonds to the surface, creating kimberlite pipes. Kimberlite is named after Kimberly, South Africa, where these pipes were first found. Most of these eruptions occurred between 1,100 million and 20 million years ago.
Kimberlite pipes are created as magma (岩浆) flows through deep fractures in the Earth. The magma inside the kimberlite pipes acts like an elevator, pushing the diamonds and other rocks and minerals through the mantle and crust in just a few hours. These eruptions were short, but many times more powerful than volcanic eruptions that happen today.
The magma eventually cooled inside these kimberlite pipes, leaving behind conical veins of kimberlite rock that contain diamonds. Kimberlite is a bluish rock that diamond miners look for when seeking out new diamond deposits. The surface area of diamond-bearing kimberlite pipes ranges from 2 to 146 hectares. Diamonds may also be found in river beds, which are called alluvial diamond sites. These are diamonds that originate in kimberlite pipes, but get moved by geological activity. Glaciers and water can also move diamonds thousands of miles from their original location.
Cutting Diamonds
There are special techniques that are used to cut and shape a diamond before it gets to the jewelry store. Diamond cutters first try to remove any impurities or irregularities in the diamond. Sometimes, diamonds have to be sawed with the use of a phosphor-bronze blade or laser. Then the diamond is rubbed by another diamond to create facets-tiny flat spots on the surface. Finally, the diamond is pressed against a rotating polishing wheel to give the diamond its finished look.
Rating Diamonds
Diamonds are judged on several factors that determine their beauty. Most diamonds never reach the consumer market because they are too flawed. Often, these diamonds are used for industrial purposes--as an abrasive, for drill bits or for cutting diamonds and other gems. If you’ve ever purchased a diamond, you’ve heard of the "4 Cs:"
1. Cut--This refers to how the diamond has been cut and its geometric proportions. When a diamond is cut, facets are created and the diamond’s finished shape is determined.
2. Clarity--This is the measurement of a diamond’s flaws, or inclusions that are seen in the diamond.
3. Carat--This is the weight of a diamond. One carat is equal to about 200 milligrams.
4. Color--In referring to transparent diamonds, the color scale runs from D to Z, beginning with Icy White-- the color of the most expensive diamonds--and ending with a light yellow.
Other unique qualities of the diamond include its transparency, luster and dispersion of light. A diamond that is created from 100-percent carbon will be completely transparent. Diamonds often contain other elements that can affect the color. Although we often think of diamonds as being clear, there are also blue, red, black, pale green, pink and violet diamonds. These colored diamonds are the truly rare ones.
Marketing Diamonds
Prior to the 1930s, diamond rings were rarely given as engagement rings. Opals, rubies, sapphires and turquoise were deemed much more exotic gems to give as tokens of one’s love. This idea of connecting diamonds to romance was captured in a brilliant ad campaign begun in the 1940s, causing demand for diamonds to increase. Surely you’ve heard the De Beers advertisement telling you that "A Diamond Is Forever." This ad campaign, which was created by the N.W. Ayer advertising agency in 1947, changed the diamond market. In 2000, Advertising Age magazine named the ad campaign the slogan of the 20th century.
Later ads by De Beers told consumers to hold onto their family’s diamond jewelry and to cherish them as a family possession--and it worked. This eliminated the aftermarket for diamonds, which further enabled De Beers to control the market. Without people selling their diamonds back to jewelers or to other people, the demand for new diamonds increased.
There are fewer than 200 people or companies authorized to buy rough diamonds from De Beers. These people are called sightholders, and they purchase the diamonds through the Central Selling Organization (CSO), a subsidiary of De Beers that markets about 70 percent to 80 percent of the world’s diamonds. De Beers sells a parcel of rough diamonds to a sightholder, who in turn sends the diamonds to cutting facilities and then to distributors. There are rough diamonds sold outside the CSO. However, the cost of these diamonds is still largely influenced by the prices set by the CSO.
Diamonds are the most coveted of all precious gems, as is witnessed by the extremely high demand for them. While this has not always been the case, diamonds are nonetheless exquisite gems that go through a long, tedious refining process from the time they are pulled from the ground to when you see them in the jewelry store. And, while some of the mystique of diamonds may be gone--they’re just carbon, after all--the diamond will likely continue to be a highly coveted jewel, because, well, "A Diamond Is Forever."
Individuals or companies buying diamonds from CSO are called ______.
选项
答案
sightholders
解析
参见“Marketing Diamonds”这一节中。这些sightholders从De Beers的子公司购买钻石再去加工,然后在市场出售。
转载请注明原文地址:https://jikaoti.com/ti/PztFFFFM
0
大学英语四级
相关试题推荐
A、Itshouldbequiet.B、Itshouldbeinthedowntown.C、Itshouldbeonthebeach.D、Itshouldhaveaswimmingpool.C事实题。从对话中可以
A、Shecan’tbookticketsforherfamilynow.B、Itishardtofindasuitablehotel.C、Shehastotakeherchildrenwithher.D、S
Inthepast,itwasbelievedthatdepression(抑郁症)wasmoreprevalentamongthepoorerandlesseducatedpeople,butthatisnot
Inmanywayswecanallbeencouragedtolearnanotherlanguage.Althoughitmayhelptohavespeciallanguagelearningabilitie
A、Toplayallsports.B、Towatchgamesandshowsofallkinds.C、Toplayandtalkaboutsportswithfriends.D、Totalkaboutspo
A、BetweenAprilandDecember.B、InApril.C、InDecember.D、Heisn’tcertain.D本题中提到两个月份。但更重要的是男士说的“No,Ihaven’t”和“I’mnotatall
Peoplecanbeaddictedtodifferentthings--e,g.,alcohol,drugs,certainfoods,oreventelevision.Peoplewhohavesuchana
A、Seventypercent.B、Fifty-fourpercent.C、Seventeenpercent.D、Fiftypercent.A
Thechairmanrequested___________(所有书面资料都要储存在电脑硬盘上).
随机试题
过冷奥氏体高温转变(在A1~550℃)的产物是()体。
A.双目镜筒中的左右两光束不平行B.不可选用复消色差物镜C.光源是紫外光D.光源是红外光E.物镜、聚光镜和光源颠倒放置体视显微镜
引起慢性阻塞性肺疾病(COPD)肺动脉高压最重要的原因是()
下列属于经理人对于股东的“内部人控制”问题表现形式的有()。
注册会计师负责对甲公司20×8年度财务报表进行审阅。在审阅过程中,注册会计师遇到下列事项,请代数做出正确的专业判断。下列各项中,注册会计师为形成审阅结论通常实施的程序有()。
通常中央处理器(CPU)和主存储器合称()。
在一定条件下进行的可逆反应:2NH3(g)N2(g)+3H2(g),下列数据能表示反应处于平衡状态的是()。
高薪技术主要特征包括()。
一位教育工作者撰文表达了她对电子游戏给青少年带来的危害的焦虑之情。她认为电子游戏就像一头怪兽,贪婪、无情地剥夺青少年的学习和与社会交流的时间。以下哪项不成为支持以上观点的理由?
下面属于白盒测试方法的是
最新回复
(
0
)