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
abrasive band
action of controller
all-bright
aluminium ethide
ambiguous case
Anaset
bottlehead
canning burst
cat tree
Cerbolite
chainwale
chloralacetoxime
Cinchona officinalis
collect one's faculty
compaignion
contection
cotton braid
cowpooling
debituminize
disultone
DPICM
Dubky
duty-paids
eccentric type vibrator
environment control in biology
evasion chart
expansion fog
explicit faith,explicit belief
family peridiniidaes
ferl
fifty cents
file layout
fink on sb
fire banked
fixed ratio (fr) schedule
flying height
garp atlantic tropical experiment (wmo/icsu) (gate)
Genseric
geopartners
Glinus
gloom-and-doomer
Godhafoss
Gorno-Chuyskiy
hailwoods
high pressure piston
Hope, R.
hostitutes
i will wait for you
infective pleurisy
intramammary pressure
iodanil
islands
kante
Larzel's anemia
legitime
leycesterias
liberal interpretation
literaryisms
Mayer sign
micronized clay
murp
musculi pterygoideus
myological
natural frequency
negativas
non-shattering glass
not give a two pins
oghma
oil-depth gauge
over-played
paler
phosacetim
picciarelli
playing-cards
postwomen
Pound, Louise
productive task
pseudacousma
purely infinite
rear parking stop and direction indicator lamps
regional sea level change
resident editor
Safe High Voltage connector
San Isidro, R.
scatologia
single thread sizing
skiable
slot tear
sphenofrontal suture
splitter switch
spot weld adhesive
sticky prices
storage adapter
straight smile
string-oriented instruction
substitutions of amino acids
swormstedt
takao
tally trade
undersea tunnel
unfledged
work of deformation