Diamonds

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Diamonds

by goelmohit2002 » Tue Jul 14, 2009 11:55 am
Edited.
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by scoobydooby » Tue Jul 14, 2009 10:36 pm
no clue. fell for E too on Q1.
whats the source?

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by goelmohit2002 » Tue Jul 14, 2009 11:28 pm
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Re: Diamonds

by ketkoag » Wed Jul 15, 2009 12:42 am
goelmohit2002 wrote:Hi All,

In the below RC Q#1, the OA is A. Can someone please tell why not E....where does appearance is talked about in the pessage ?

================================================
Diamonds are almost impos-
sible to detect directly because they
are so rare: very rich kimberlite
pipes, the routes through which
(5) diamonds rise, may contain only
three carats of diamonds per ton
of kimberlite. Kimberlite begins as
magma in Earth’s mantle (the layer
between the crust and the core). As
(10) the magma smashes through layers
of rock, it rips out debris, creating
a mix of liquid and solid material.
Some of the solid material it brings
up may come from a so-called
(15) diamond-stability field, where condi-
tions of pressure and temperature
are conducive to the formation of
diamonds. If diamonds are to sur-
vive, though, they must shoot toward
(20) Earth’s surface quickly. Otherwise,
they revert to graphite or burn.
Explorers seeking diamonds look
for specks of “indicator minerals”
peculiar to the mantle but carried up
(25) in greater quantities than diamonds
and eroded out of kimberlite pipes
into the surrounding land. The stan-
dard ones are garnets, chromites,
and ilmenites. One can spend years
(30) searching for indicators and tracing
them back to the pipes that are their
source; however, 90 percent of
kimberlite pipes found this way are
barren of diamonds, and the rest
(35) are usually too sparse to mine.
In the 1970’s the process of
locating profitable pipes was refined
by focusing on the subtle differ-
ences between the chemical
(40) signatures of indicator minerals
found in diamond-rich pipes as
opposed to those found in barren
pipes. For example, G10 garnets,
a type of garnet typically found in
(45) diamond-rich pipes
, are lower in
calcium and higher in chrome than
garnets from barren pipes. Geo-
chemists John Gurney showed that
garnets with this composition were
(50) formed only in the diamond-stability
field; more commonly found ver-
sions came from elsewhere in the
mantle. Gurney also found that
though ilmenites did not form in the
(55) diamond-stability field, there was a
link useful for prospectors: when
the iron in ilmenite was highly
oxidized, its source pipe rarely
contained any diamonds. He rea-
(60) soned that iron took on more or less
oxygen in response to conditions in
the kimberlitic magma itself—mainly
in response to heat and the avail-
able oxygen. When iron became
(65) highly oxidized, so did diamonds;
that is, they vaporized into carbon
dioxide.



Q1....Each of the following is mentioned in the passage as a difference between G10 garnet and other versions of garnet EXCEPT

A. level of oxidation
B. commonness of occurrence
C. chemical signature
D. place of formation
E. appearance in conjunction with diamonds

[spoiler]OA = A...[/spoiler]

Q2....The passage suggests that the presence of G10 garnet in a kimberlite pipe indicates that
A. the pipe in which the garnet is found has a 90% chance of containing diamonds
B. the levels of calcium and chrome in the pipe are conducive to diamond formation
C. the pipe passed through a diamond-stability field and thus may contain diamonds
D. any diamonds the pipe contains would not have come from the diamond-stability field
E. the pipe’s temperature was so high that it oxidized any diamonds the pipe might have contained

[spoiler]OA = C[/spoiler]
The bold part in lines 43- 47 above in the passage states the appearance of G10 in conjunction with diamond..

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by scoobydooby » Wed Jul 15, 2009 12:55 am
ah, thanks ketkoag. so "appearance" here actually means location/existence. i had been thinking of appearance as the look/noticeable physical attribute.

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by goelmohit2002 » Wed Jul 15, 2009 2:49 am
Edited.
Last edited by goelmohit2002 on Sun Aug 16, 2009 8:19 pm, edited 1 time in total.

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by scoobydooby » Wed Jul 15, 2009 3:05 am
ketkoag is spot on.

mhit, we missed out on the way the word "appearance" seems to be have been used here. here it means garnets come in diamond rich pipes

https://dictionary.reference.com/browse/appearance

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by goelmohit2002 » Wed Jul 15, 2009 5:23 am
Edited.
Last edited by goelmohit2002 on Sun Aug 16, 2009 8:19 pm, edited 1 time in total.

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by aspirant_gmat » Wed Jul 15, 2009 7:50 am
I agree that E is not mentioned in the passage but A should be the answer because A talks about ilmenite not garnet.

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by goelmohit2002 » Wed Jul 15, 2009 8:30 am
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by aspirant_gmat » Wed Jul 15, 2009 11:24 am
Hey goelmohit2002!

I think you are right. Yet, I chose A because I thought it was a better choice than E, which it's not even about garnet.

And as others have already indicated -

"appearance in conjunction with diamonds" may mean " found in co-occurance with diamonds OR being present with diamonds", which is true about G10 garnet(It's noramlly found with diamonds).

As given in the dictionary:

Conjunction:
the state of being conjoined; union; association: The police, in conjunction with the army, established order.
Appearance:
1.the act or fact of appearing, as to the eye or mind or before the public: the unannounced appearance of dinner guests; the last appearance of Caruso in Aïda; her first appearance at a stockholders' meeting.

Hope it helped.[/img]

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by goelmohit2002 » Wed Jul 15, 2009 11:33 am
Edited.