Diamonds are almost impos- sible to detect directly

Anybody wants to try this one?

1 - D

2 - A

3 - C

4 - C

(1)The primary purpose of the passage is to
A. discuss an objection to Gurney’s theories about the uses of indicator minerals
Definitely not
B. explore the formation of diamonds and the reasons for their scarcity
yes, but not the main purpose
C. analyze the importance of kimberlite pipes in the formation of diamonds
Again not the main purpose
D. define the characteristics of indicator minerals under differing conditions
Yes he did that, but still it's not the purpose
E. explain a method of determining whether kimberlite pipes are likely to contain diamonds
Yes


(2)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
This is mentioned for the ilmenites, instead of the garnet
B. commonness of occurrence
C. chemical signature
D. place of formation
E. appearance in conjunction with diamonds

(3)
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
No number is mentioned
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
Definitely out
E. the pipe’s temperature was so high that it oxidized any diamonds the pipe might have contained
oxidization is not mentioned when talk about garnet

(4)
According to the passage, Gurney refined the use of ilmenites in prospecting for diamonds in which of the following ways?
A. He found that ilmenites are brought up from the mantle by kimberlite pipes and erode out into the surrounding land in greater quantities than diamonds.
Not helping
B. He found that since ilmenites do not form in the diamond-stability field, their presence indicates the absence of diamonds.
Not all ilmenites, but the ones with highly oxidized iron
C. He showed that highly oxidized iron content in ilmenites indicates a low survival rate for diamonds.
Thus this one is correct
D. He found that when the iron in ilmenites is highly oxidized, conditions in the magma were probably conducive to the formation of diamonds.
It's the opposite
E. He showed that ilmenites take on more or less oxygen in the kimberlite pipe depending on the concentration of diamonds.
What are you talking about

Thanks all , here is the OA

1, E

2, A

3, C

4, C


Congratulations, HongHu, it seems like you're ready for the test.

Thank you! I haven't even prepared anything for RC and CR. Was counting on my basic skills.

Hmmm, we have very differing answers here. This is one of those dreaded science passages The reason I took 1-B is because of the very first sentence which describes the tone of the passage.
One can spend years

To me, (D) and (E) are more representative of the second half of the passage. Overall, we are talking about the scarcity of diamonds.

Chunjuwu, were there paragraphs in this passage? It would be good if they were separated into paragraphs accordingly.

Thanks Paul.

Now I have is only pdf file.

If I have, I will share with you.

wow, good job honghu, just realized I took too much time to go over the question before the answer got posted. Well, I am dumbfounded

But your grammar skills still PWNs everyone of us. (Yes you can see that I've been wandering around teh internet. ) And I can hardly get about half of the grammar questions right. So there. And we share our best tricks so we can collectively PWN the GMAT.

Yup, I think RC was/is my downfall. If I take the GMAT again, I will know what to really focus on

I got C, E, C, C......Honghu, for ques 2 where in the passage "E" is mentioned abt differences in garnet ??

Also for ques 1....seems like only latter half of the passage mentions a method of determining whether kimberlite pipes are likely to contain diamonds.....I am not convinced that this is the main idea of the passage. Doesn't seem like author set out to write this passage to mention a method only, thoughts ?.....

"G10 garnets, a type of garnet typically found in diamond-rich pipes"
Meaning garnets appear in conjunction with diamonds.


Hmm I don't know how to talk about this. Basically we can shorten the paragraph like this:

Diamonds are very important. Because of the way they are formed we can use some other things to locate diamonds. But it is still hard to locate them. This person, however, discovered a couple neat ways so that it isn't so hard to find diamonds now.

So what is the purpose of this paragraph? It talks about diamonds, yes, but not everything about diamond. It's about how to find them. And more specifically, the method that makes it easy to find them.

I see why I was wrong in ques 2...I thot "appearance in conjunction of diamond" meant garnets that have a look and feel of diamonds....didn't understand the sentence atall. But I am still not convinced that the main idea is to explain one method to find diamonds

why do ppl post such passages without questions?

Incomplete passage...request the moderator to remove

1)Diamonds are almost impossible to detect directly because they are so rare:
very rich kimberlite Line pipes, the routes through which (5) diamonds rise, may contain only three carats of diamonds per ton
of kimberlite. – (EXPLAINS THE FIRST LINE (NOTICE THE COLON AFTER THE LINE)
Introductory lines emphasize on kimberlite and inform that these pipes may contain only a small percentage of diamond. Rest of the passage expand on this-
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 conditions of pressure and temperature are conducive to the formation of diamonds.- (EXPLAINS THE KIMBERLITE PROCESS). If diamonds are to survive, 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.....The entire passage focus on the kimberlite pipes and how likely they are to contain diamonds. Formation of diamond and their scarcity is also explained in regard of Kimberlite only and hence E becomes the primary purpose.
2)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 - Correct, used to describe properties of ilmenites
B. commonness of occurrence - Incorrect, a type of garnet typically found in diamond-rich pipes
C. chemical signature - Incorrect, are lower in calcium and higher in chrome than garnets from barren pipes.
D. place of formation - Incorrect, Geochemists John Gurney showed that garnets with this composition were formed only in the diamond-stability field
E. appearance in conjunction with diamonds - Incorrect, a type of garnet typically found in diamond-rich pipes
3)The word "suggests" indicates that this is an Inference question, so we'll need to
1) re-read the pertinent info in the passage and try to make a prediction, and
2) select the answer choice that is closest to the tiny details from the passage.
Where is "presence of G10 garnet in a kimberlite pipe" mentioned?
I see it in the second paragraph: ...the process of locating profitable pipes was refined by focusing on the subtle differences between the chemical 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 diamond-rich pipes, are lower in calcium and higher in chrome than garnets from barren pipes. Geochemists John Gurney showed that garnets with this composition were formed only in the diamond-stability field.
So, what does LOW calcium/HIGH chrome indicate? Probably a profitable pipe!
Prediction: $$$. The correct answer is (C).
4)A. He found that ilmenites are brought up from the mantle by kimberlite pipes and erode out into the surrounding land in greater quantities than diamonds.
B. He found that since ilmenites do not form in the diamond-stability field, their presence indicates the absence of diamonds.
C. He showed that highly oxidized iron content in ilmenites indicates a low survival rate for diamonds. Correct, When iron became highly oxidized, so did diamonds; that is, they vaporized into carbon dioxide.
D. He found that when the iron in ilmenites is highly oxidized, conditions in the magma were probably conducive to the formation of diamonds.
E. He showed that ilmenites take on more or less oxygen in the kimberlite pipe depending on the concentration of diamonds.