时间:2018-12-01 作者:英语课 分类:自考英语(一)78讲


英语课













 






  Scientists know that the combination of extreme heat and pressure changes carbon into diamonds. Such heat and pressure exist only in the hot, liquid mass of molten rock deep inside the earth. It is thought that millions of years ago this liquid mass pushed upward through cracks in the earths crust. As the liquid cooled, the carbon changed into diamond crystals.
      There are only four areas where very many diamonds have been found.
      The first known(famous) area was in India, where diamonds were found thousands of years ago. In the 1600s, travelers from Europe brought back these beautiful stones from India. Diamonds became very (be)popular with the kings and queens of Europe.
      In the 1720s, diamonds were discovered in Brazil. This discovery came at a good time, too. Indias supply of diamonds was finally running out after 2,500 years of mining the stones.
      In the 1800s, two other important areas were found in Russia and South Africa. Today, most diamonds used in industry come from Russia. Most diamonds used as gems 1 come from South Africa. only twenty-five percent of all diamonds mined are good enough for cutting into gems.
      Most of the diamonds in India were found in stream beds. people would pick up handfuls of gravel 2 from the bottom of the streams and sort out the diamonds. These diamonds were probably carried from where they were formed to India by great sheets of moving ice that covered parts of the earth 20,000 years ago.
      Most diamonds today are not found in stream beds, however. They are mined from rock formations deep inside the earth called pipes. Scientists believe that these are parts of volcanoes that were formed when molten rock pushed upward through the earths crust. The hard rock in which diamonds are found is called blue ground, because it is somewhat blue. The blue ground is blasted into large pieces of rock which are carried to the surface by elevator. Then the rocks are carefully crushed so that the diamonds are not destroyed. Next, the crushed material is taken over to washing tables. Here, it flows over boards thickly coated with grease. Since diamonds stick to grease, they are left behind by the rocks and mud which flow down the tables.
   
  It is said eportedestimatedknown
  Well-known----unknown
  He is a well-known musician.
  Unknown number
  pick out
  I will pick out 10 of you to attend the contest.
   


 



1 gems
growth; economy; management; and customer satisfaction 增长
  • a crown studded with gems 镶有宝石的皇冠
  • The apt citations and poetic gems have adorned his speeches. 贴切的引语和珠玑般的诗句为他的演说词增添文采。
2 gravel
n.砂跞;砂砾层;结石
  • We bought six bags of gravel for the garden path.我们购买了六袋碎石用来铺花园的小路。
  • More gravel is needed to fill the hollow in the drive.需要更多的砾石来填平车道上的坑洼。
学英语单词
Alizay
andira inermiss
antiblue
antihedonism
archabbot
archin(e)
aroun
asparty-L-histidine
assembler machine
automatic computer
bear-pit
bore diameter of roller and cage thrust assembly
bouncinesses
brown v board of education
business expenditures for new plant and equipment
cantilever for basket
capacitacin
chromosomal RNA
column fractionating
critical regionalism
cyclic fatigue
dilatory
diplophase
directed edges
engaging piece
eoples
ersbyite (meiomite)
Eunectes murinus
feebates
fixed assets cost
fly right
food sources
genitourinary fistula
geometric locus
gielgud
gift-giving ritual
herpetineuron wichurae(broth)card.
Holmes's sign
hybrid storm
Inchkeith
including overtime
indian rupee
insaturity
inter-sectoral division of labour
intercoordination
jasminum prubescens willd.
K-back
least square solution
leib
level gage
lightwave
listeria meningitis
Lomnice nad Popelkou
lose concentration
low power objective
macrotrichia
Madhya Pradesh
magmatic
magnetic fault detection
margent
marketing risks
menaced
minimal space
moderately volatile fuel
money talks, bullshit walks
mortonagrion hirosei
nonlinear taper
object relation theory
octingentenary
opern
optical enlargement
perfluoro-
polarization spectroscopy
proportional weir
prospective path
Purkinje's phenomenon
Pyrus hopeiensis
quitclaimance
reciprocable motor
Red Pt.
relationists
repumping
running time
sap vesicle
single equation regression prediction
smallpox cake
spangled coquette
splash-landed
st. vincent and the grenadiness
standard test for glass viscometer
structural platform
table calculation
touchscreen
twenty-somethings
two-years
UHF converter
Upper Cretaceous
vent-type injection moulding
warm regards
wave-modulated oscilloscope tube
Yamakoshi
zero-access instruction