Diamonds are almost impossible to detect directly because they are so

Question

Diamonds are almost impossible to detect directly because they are so rare: very rich kimberlite pipes, the routes through which 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 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 diamond-stability field, where conditions of pressure and temperature are conducive to the formation of diamonds. If diamonds are to survive, though, they must shoot toward 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 in greater quantities than diamonds and eroded out of kimberlite pipes into the surrounding land. The standard ones are garnets, chromites, and ilmenites. One can spend years 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 are usually too sparse to mine.
 
 In the 1970’s 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; more commonly found versions came from elsewhere in the mantle. Gurney also found that though ilmenites did not form in the 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 reasoned that iron took on more or less oxygen in response to conditions in the kimberlitic magma itself—mainly in response to heat and the available oxygen. When iron became highly oxidized, so did diamonds; that is, they vaporized into carbon dioxide.   1 
 E 
1.The primary purpose of the passage is to

(A) discuss an objection to Gurney's theories about the uses of indicator minerals
(B) explore the formation of diamonds and the reasons for their scarcity
(C) analyze the importance of kimberlite pipes in the formation of diamonds
(D) define the characteristics of indicator minerals under differing conditions
(E) explain a method of determining whether kimberlite pipes are likely to contain diamonds

2 
 A 
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
(B) commonness of occurrence
(C) chemical signature
(D) place of formation
(E) appearance in conjunction with diamond

3 
 C 
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
(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

4 
 C 
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.
(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.
(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

5 
 D 
5.Which of the following best describes the primary purpose of the second paragraph of the passage?

(A)It describes a method of diamond formation different from the one described in the first paragraph.
(B)It gives examples of the ways in which a method for locating diamonds may be applied to other gems.
(C)It gives examples of exceptions to the natural phenomenon of diamond formation as described in the first paragraph.
(D)It discusses an improvement to the process of diamond prospecting described in the first paragraph.
(E)It challenges the scientific foundation of the method of diamond prospecting described in the first paragraph.

Nightfury14 · Accepted Answer

Timer : 10min 43sec

1) The primary purpose of the passage is to 
 A.  discuss an objection to Gurney’s theories about the uses of indicator minerals
 Incorrect , as Gurney's theories are discussed only in the last 10-15 lines of the Paragraph.

B.  explore the formation of diamonds and the reasons for their scarcity
 Incorrect , no details regarding formation of diamonds is given.

C.  analyze the importance of kimberlite pipes in the formation of diamonds
 Incorrect , the passage describes relation between the kimberlite pipes and the diamond. It does state the importance anywhere.

D.  define the characteristics of indicator minerals under differing conditions
 Incorrect , Indicator minerals surface only in the second half of the passage. Also the characteristics of Indicator mineral are not discussed in  "Differing Conditions"

E. explain a method of determining whether kimberlite pipes are likely to contain diamonds 
 Correct , the passage starts with the discussion of Kimberlite pipe, their formation, their characteristics and their relation with "Indicator Minerals".

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 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-  Incorrect , One can spend years 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 are usually too sparse to mine.No reference of G10 w.r.t. 90%.

B.  the levels of calcium and chrome in the pipe are conducive to diamond formation -  Incorrect , are lower in calcium and higher in chrome than garnets from barren pipes. Passage and Choice B mean different.

C.  the pipe passed through a diamond-stability field and thus may contain diamonds.  Correct , Geochemists John Gurney showed that garnets with this composition were  formed only in the diamond-stability field ;

D.  any diamonds the pipe contains would  not  have come from the diamond-stability field.  Incorrect

E.  the pipe’s temperature was so high that it oxidized any diamonds the pipe might have contained.  Incorrect , the oxidation is referred to Ilemnite and not 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.
 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.

Goodluck

Linhbiz · Answer

Q1- The primary purpose of the passage is to

Before going to answer the question, my quick summary to the passage:

Diamonds are rare & hard to detect --> only through "kimberlite pipes" can have diamond --> prev: several ineffective ways to decide which kimberlite pipes have good potential of containing diamond --> later: Gurney's method is more effective.

So now to the answer:

(A)discuss an objection to Gurney's theories about the uses of indicator minerals  - incorrect, if any the passage actual supports Gurney's method 
(B)explore the formation of diamonds and the reasons for their scarcity  - a little bit on the formation of diamond in the first passage, but the rest are all about how to identify rich diamond "kimberlite pipes". Moreover, passage only said diamon are rare - doesn't say anything about why they're rare --> incorrect! 
(C)analyze the importance of kimberlite pipes in the formation of diamonds  -> very little discuss if any, the important of something at best should be compare with some other similar things, here, I don't see any of other similar thing, diamond is only through "kimberlite pipes" --> so, incorrect! 
(D)define the characteristics of indicator minerals under differing conditions --> nope
(E)explain a method of determining whether kimberlite pipes are likely to contain diamonds  --> yep, this could be one, 1st passage does talk about  Explorers seeking diamonds look for specks of “indicator minerals”  and then elaborates more about it, the 2nd passage explore another more effective way to seek diamond in kimberlite pipes --> Correct!

Q2. 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 diamond

This is a tough & tricky one, I need to infer some of the information from the passage:

First, take a look at the 1st passage

“indicator minerals”  peculiar to the mantle but carried up in greater quantities than diamonds and eroded out of kimberlite pipes into the surrounding land. The  standard ones are garnets , chromites, and ilmenites. 
 
--> so, I can infer that standard characteristic of a possible diamond mine must include garnets 
Therefore, there is a conjunction (or good probability of appear together) between garnets & diamond
--> Hence, (E) is out

Second, take a look at the 2nd passage again:

focusing on the subtle differences between the  chemical signatures  of indicator minerals.  --> so (C) is out

garnets with this composition were formed only  in the diamond-stability field   - it talked about a place of formation (diamond-stability field) --> so (D) is out

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. 
- there is an occurrence of garnets in difference pipes but some are more of Ca & Cr than other, could we hence infer that it's talking about how often you can find a type of garnets in different pipes --> so it does talk about commonness of occurrence, however, not too clear --> leave it to 50/50 chance.

So, we only left with A & B!

Read further, the rest of the passage only talk about iron and oxidation, nothing mention about garnets.

So,  in all, (A) is more persuasive than B --> choose correct answer A

Alpach · Answer

Question 2:

I just selected sentences that can help to detect the differences between the 2 types of garnet.

(A)level of oxidation : the passage mentioned the level of occidation as a peculiarity of iron solely.

(B)commonness of occurrence -> Diamonds are almost impossible to detect directly because they are so  rare  ... garnets with this composition were  formed only in the diamond-stability field ; more commonly found versions came from elsewhere in the mantle

(C)chemical signature -> by focusing on the subtle  differences between the chemical signatures  .... For example, G10 garnets, are lower in calcium and higher in chrome than garnets from barren pipes

(D)place of formation -> more commonly found versions came from elsewhere in the mantle

(E)appearance in conjunction with diamond -> garnets with this composition were formed only in the diamond-stability field

Hope it helps !

pankajjindal25 · Answer

The primary purpose of the passage is to
(A)discuss an objection to Gurney's theories about the uses of indicator minerals
(B)explore the formation of diamonds and the reasons for their scarcity
(C)analyze the importance of kimberlite pipes in the formation of diamonds
(D)define the characteristics of indicator minerals under differing conditions
(E)explain a method of determining whether kimberlite pipes are likely to contain diamonds

Why answer is E and not B ?

Marcab · Answer

There is always a difference between the scope of a passage and the reason for writing a certain passage.
B covers everything in the passage, but what it not covers is the intention of the author as to why he/she wrote the passage. Thereby B is the scope and e is the primary purpose of the passage.

saumya12 · Answer

B says: "explore the formation of diamonds and the reasons for their scarcity".

There is actually no where in the passage that "formation of diamonds" has been explored. The only reference of diamond formation is in regards to "diamond-stability field" (where conditions of pressure and temperature are conducive to the formation of diamonds).

The passage is about kimberlite pipes, how most of them are barren and how some techniques (differences between the chemical signatures of indicator minerals in kimberlite pipes) can help to increase the "hit ratio".

Poorvasha · Answer

Hi, mikemcgarry , chetan2u , VeritasPrepKarishma , GMATNinja , sayantanc2k Can you please help with the below question: 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 diamond Can you help me identify the evidence from the passage to rule out option E ? Thanks in advance

chetan2u · Answer

HI...

it is given in the coloured portion above that G10 are found in diamond rich pipe whereas the other garnet in barren pipe..
so G10 appears in conjunction with diamond..

choice E means G10 appearing along with diamond. 
May be one can get confused in literal meaning of APPEARANCE as LOOKS

lakshya14 · Answer

Does "levels" in Q3. only means "high levels"? The paragraph says the number of diamonds depends on the level of the calcium and chrome irrespective of high or low.

bM22 · Answer

Hi  lakshya14 ,

Question 3 asks what does the presence of G10 garnet in a kimberlite pipe indicate. It can be inferred from the lines:
"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; ",implying that G10 garnet is found in diamond rich pipes, lower in calcium and higher in chrome, in turn implying that the pipe passed through a diamond-stability field.

I believe your doubt is related to option B. Levels doesn't necessarily mean "high levels" only it could mean low level as well. Option B is incorrect because of the word conducive as it gives a different meaning to the sentence. We can't infer if levels of calcium and chrome in the pipe play a part in diamond formation. We can only infer that one of “indicator minerals” garnets is found in diamond-rich pipes are lower in calcium and higher in chrome than garnets from barren pipes.

Hope This Helps.
Thanks.

avigutman · Answer

Video solution from Quant Reasoning: Subscribe for more: https://www.youtube.com/QuantReasoning? ... irmation=1 https://www.youtube.com/watch?v=lxTbINgq2JY

Finesse · Answer

HarshavardhanR 
Can you please explain question 1 - E vs C

HarshavardhanR · Answer

Sure. My take!

C:  analyze the importance of kimberlite pipes in the formation of diamonds

My main issue with choice C:  I do not think kimberlite pipes are even involved in the "formation of diamonds". The passage does not suggest that these pipes are involved in the creation process of the diamonds.

- Kimberlite pipes are the routes  through which diamonds rise .
- As the magma rips smashes through layers of rock, it rips out solid material, some from a diamond-stability field. So, clearly, among the rock layers are places where diamonds get formed. Kimberlite magma rips out some of this solid material, thus, introducing diamonds into the pipeline.

The passage does not even suggest that kimberlite pipes are involved in diamond formation, forget this being the primary purpose of the passage.

Even if we say - "analyze the importance of K pipes with regards to diamond mining", this would not be the primary purpose.

Observe that the passage

- Introduced K pipes as the place where diamonds can be found. But beyond this, the passage is an exploration of "how to identify pipes worth exploring for diamonds". Explorers seeking diamonds looking at  indicative minerals  ---- in the first para --- introduces the method. The second para is all about improvements to the method (finer nuances of indicative minerals).

E is the best choice.

---
Harsha

Finesse · Answer

Thanks! - I was confused because I was solving on another platform and the answer was given as C there - Makes sense and clears my confusion

glagad · Answer

Hello - My Contention with Question 1, Option E is that

"explain a method of determining whether kimberlite pipes are likely to contain diamonds"

The passage as a whole doesn't really explain the nuance differences in detecting the presence of Diamond using the indicator materials, but only the second passage does.

First paragraph, only presents the problem to an extent.

How can this be the right answer here?

Diamonds are almost impossible to detect directly because they are so

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Diamonds are almost impossible to detect directly because they are so

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