Colorless diamonds can command high prices as gemstones. A type of

Best place to start here is with the conclusion. We're trying to find the "serious flaw" in this thing:

Great. And here's the key piece of evidence that supports the conclusion above:


In short, we're trying to figure out why there might be a disconnect between two statements: 1) only 2% of diamonds are of the colored type that can be successfully treated, and 2) the vast majority of colorless diamonds sold by jewelers are naturally colorless.

So why are (D) and (E) wrong? (D) essentially indulges a hypothetical, suggesting that in the future, there may be other methods for "making colorless diamonds from colored ones." That's completely irrelevant to the conclusion, which is concerned solely with the diamonds currently sold by jewelers. Future technologies do nothing to weaken that conclusion.

(E) is concerned with the difficulty of distinguishing a naturally colorless diamond from a treated one. But this is completely irrelevant to the question: we're concerned with figuring out why the conclusion ("the vast majority of colorless diamonds sold by jewelers are naturally colorless") might be flawed given the key premise (only 2% of diamonds mined could be treated). Sure, it can be hard to tell the difference between treated and naturally colorless diamonds -- but (E) does nothing to tell us why that conclusion might be wrong. If the treatable colored diamonds are indeed scarce, the conclusion could easily still hold -- regardless of how hard it is to recognize a treated diamond.

I hope this helps!

Hi,

Thanks for the specific explanation for the correct answer.

As per the Official Guide, still am not sure the explanation for wrong answers, as understanding the individual options would help POE to get the correct answer.

HelloSapient,
Conclusion:the vast majority of colorless diamonds sold by jewelers are naturally colorless.
Premise: However, only 2 percent of diamonds mined are of the colored type that can be successfully treated, and many of those are of insufficient quality to make the treatment worthwhile

Analysis :If the availability of naturally colorless diamonds is less then the colored type that can be successfully treated ,then the vast majority of the colorless diamonds ca be the treated one .

Only Answer Choice B talks about the availability of the naturally colorless diamonds with respect to the colored type.

Let me know if you have any further doubts.

Hope the attached explanation makes sense

GMATNinja in D how come you came with the logic that the methods are in future?? I thought there were alternative methods already in place not mentioned in the premisE which may be much better??

deependra1234,
Notice that choice D specifically refers to "the currently available method for making colorless diamonds":
Thus, choice D does not imply, as you put it, that there are "alternative methods already in place"; rather, it suggests that in addition to the currently available method, there might be other possible methods that are NOT currently available (for example, a method that should work in theory but has never been put into practice). Since those alternative methods are not currently available, they have no impact on the author's argument, which deals with the diamonds currently sold by jewelers. Those alternative methods could only impact future scenarios (ie once those methods become available).

I hope that helps!

Hi mikemcgarry, GMATNinjaTwo, GMATNinja, MagooshExpert Carolyn, sayantanc2k,
I became confused after reading this thread.

(D) the currently available method for making colorless diamonds from colored ones is treated as though it werethe only possible method for doing so

the highlight words "it were" imple an subjunctive mood, in other words, D implies the currently available method is impossible only method. then, i interpretate that there are many methods except currently available methods,
so there are many ways to increase the quatity of treated diamonds, leading the argument invalid.
it is a flaw in the assumption.

Please point out my fault.

Appreciate it

Have a nice day.
>_~

Choice (D) distinguishes between 1) the currently available method and 2) other possible methods. The wording suggests that there is only one method currently available, even though there might be several other possible methods that are not currently used.

So, yes, there might be other possible methods, but none of those are currently available. The argument is only concerned with diamonds that are currently sold by jewelers, so we are only concerned with the currently available method.

Thus, (D) is irrelevant and can be eliminated.

I hope that helps!

Choice (B) distinguishes between 1) the currently available method and 2) other possible methods. The wording suggests that there is only one method currently available, even though there might be several other possible methods that are not currently used.

So, yes, there might be other possible methods, but none of those are currently available. The argument is only concerned with diamonds that are currently sold by jewelers, so we are only concerned with the currently available method.

Thus, (D) is irrelevant and can be eliminated.

I hope that helps![/quote]

Hi GMATNinja


Would you please further explain this ?
My interpretation of B is that
the currectly available for making colorless diamonds from colored ones is treated the only possible method for doing so, as though the currently available method were the only possible method,
from the subjunctive mood in the sentence, i infer the currently available method is not the only one.

Seems i missed something, i am afraid i did not catch your clarification of B.

Please ~~~

Have a nice day

zoezhuyan, they aren't trying to trick you with verb mood here

Yes, choice (D) does suggest that the currently available method is not the only one... but that does NOT mean that the other possible methods are currently available.

I think you are interpreting choice (D) like this: "the currently available method for making colorless diamonds from colored ones is treated as though it were the only AVAILABLE method for doing so."

(D) does NOT tell us that there are other AVAILABLE methods. Instead, it tells us that other methods are POSSIBLE. Until those other methods are actually developed/implemented, the current method will be the only one available.

Just because something is possible does not mean it is available.

I hope that helps!

Colourless diamonds are expensive.
Some coloured diamonds can be made colourless (and presumably sold at high price)
Only 2% of diamonds mined (including coloured and colourless) are treatable and even fewer (say just 1% of all diamonds mined) are good enough to make it worthwhile.

Conclusion: Vast majority of colourless diamonds sold by jewellers are naturally colourless.

There is a problem here. When we talk about the numbers 2% and 1%, we are talking about the set of all diamonds mined. In our conclusion, we are talking about the set of diamonds that are sold by the jewellers. Without knowing how big the set of diamonds sold by jewellers is, we cannot make the comparison.

Say total diamonds mined = 1000
Out of these, say 100 are naturally colourless.
Another 10 (1%) are coloured but profitably treatable.
So the jewellers could be selling 110 diamonds out of which the vast majority (100) could be naturally colourless.

Say total diamonds mined = 1000
Out of these, say 5 are naturally colourless.
Another 10 (1%) are coloured but profitably treatable.
So the jewellers could be selling 15 diamonds out of which the vast majority (10) are coloured but treated.

Hence, whether our conclusion works or not, depends on what % of all diamonds mined are naturally colourless.

(A) comparisons between the price diamonds command as gemstones and their value for other uses are omitted
Other uses are irrelevant.

(B) information about the rarity of treated diamonds is not combined with information about the rarity of naturally colorless, gemstone diamonds
Correct. As discussed above, we need info on rarity of naturally colourless diamonds to reach our conclusion.

(C) the possibility that colored diamonds might be used as gemstones, even without having been treated, is ignored
We are talking about colourless diamonds as gemstones. Irrelevant to our conclusion.

(D) the currently available method for making colorless diamonds from colored ones is treated as though it were the only possible method for doing so
We are talking about the current scenario only and the currently available method only.

(E) the difficulty that a customer of a jeweler would have in distinguishing a naturally colorless diamond from treated one is not taken into account
The argument says that only sophisticated tests can differentiate. This doesn't have anything to do with our conclusion.

Answer (B)

After I solve CR questions under a time constraint, I can't resist myself to delve into tasty 700-level questions, and this question is no exception.

I would like to know that if we apply a subtle change to option D, will it be a flaw in the reasoning as well? Please refer below to see the modification.

The currently available method for making colorless diamonds from colored ones is treated as though it is were the only possible method for doing so.

tyildirim92
That modification wouldn't change the meaning of D. "As though it were" just indicates a hypothetical; it isn't the past tense, despite the use of "were." Similarly, we might say "If this sandwich were bigger, I wouldn't be able to finish it." We aren't talking about the past.

In any case, D has no effect on the argument because the reasoning in the argument doesn't rely on a particular method of creating colorless diamonds. The author simply states that only 2% can be treated. If in the future, a new method comes around, the author may have to change their reasoning, but that doesn't affect what's on the market now. In the meantime, we have to accept the premise that only 2% can be treated (by whatever means are available), so it doesn't matter if they can be treated in different ways.

Hi GMATNinja,

First of all, thank you for your explanation on why option D is wrong.

But because I am not a native speaker, I would like to confirm my understanding of your explanation. Please help me to confirm whether my understanding is correct.

In the argument, the author talks about one method which is, let say, bleaching color diamonds to get colorless diamonds. Then, he reasons that using this method will generate very small quantity of bleached colorless diamonds. Finally, he concludes that majority of colorless diamonds currently sold in the market are naturally colorless.

From that argument, I think the author assumes two things for the argument to stay correct: i) the number of colorless diamonds currently sold is far more than the number of bleached diamonds, and ii) other methods (let's take an example: using pressure to form artificial colorless diamonds in the labs), if available, cannot produce sufficient quantity to match the currently sold number.

Now back to option D, which proposes a flaw of the argument, "the currently available method" implies that there is only one method to make artificial colorless diamonds (i.e. bleaching diamonds), other methods are not currently available. But what if, there are other now available methods that can generate a big number of artificial colorless diamonds, then I think the argument in the question will fall. So can we consider D an flaw of the argument? or cannot because it does not go far enough?

I have read the explanation from OG: "The argument only concerns the types of colorless diamonds sold now, not the types that may be sold in the future if other treatment methods are discovered" but cannot understand how option D implies about future methods. Yet I am not a native speaker so would you please help me to understand true meaning of option D? so that I will understand what was wrong with my comprehension and reasoning.

Thank you so much.
Tin

You've got a contradiction in your explanation:

" "the currently available method" implies that there is only one method to make artificial colorless diamonds (i.e. bleaching diamonds), other methods are not currently available. But what if, there are other now available methods that can generate a big number of artificial colorless diamonds"...

You're right that by using "the," (D) tells us that, at this moment in time, there is only ONE way to make artificial colorless diamonds. So, it doesn't make sense to ask "what if there are other methods available now?" (D) tells us that there is currently only one way to make artificial colorless diamonds.

Then, (D) goes on to say that this ONE method "is treated as though it were the only possible method for doing so."

If there's currently only ONE method, then other "possible" methods must be ones that have not yet been discovered. For instance, maybe the current method is bleaching. But perhaps there is another way -- let's say, chemical extraction. Well, that method might be totally possible, but it's not currently in use. Because it's not currently in use, the author's argument about colorless diamonds sold NOW is not at all impacted by this alternate "possible" method.

In addition, it's a dangerous game to pick out assumptions in the argument yourself, instead of just assessing whether each answer choice points out a flaw in the reasoning of the argument. Here, would the existence of another method even hurt the argument that much? The author focuses on: 1) the percentage of colored diamonds that can be treated, and 2) the quality of those diamonds.

Neither of those factors are impacted by the existence of another method. For (D) to really point out a flaw, we'd need to know that not only is there another method CURRENTLY available, but also that it is significantly CHEAPER than the method explored in the passage.

(D) simply doesn't give us that information, so it's not a flaw in the argument's reasoning.

I hope that helps!

I don't understand how the rarity of naturally occurring diamond flaws the conclusion.
It's completely possible that even if the naturally occurring diamonds are rare , the diamonds being sold by the shopkeepers are natural and original.

Just because something is rare doesn't mean its being perjured and sold. It has not been mentioned that the quantity of original diamonds being sold are more than the quantity known to exist.

Can someone explain me this ? GMATNinja

The problem is that the argument assumes that because treated colorless diamonds (CDs) are rare, they must make up a small percentage of the total CDs that are sold. But what if natural CDs are even more rare than treated CDs? If that’s the case, then treated CDs, although rare among all diamonds, will make up a majority of the CDs that are sold.

In other words, the argument is flawed because it doesn’t consider how rare natural CDs may be. They could be even more rare than treated CDs, and the argument overlooks that possibility. That is exactly what (B) says, so it is the best answer choice.

I hope that helps!