Colorless diamonds can command high prices as gemstones. A type of less valuable diamonds can be treated to remove all...

GMAT Critical Reasoning : (CR) Questions

Source: Official Guide

Critical Reasoning

Misc.

MEDIUM

...

Notes

Post a Query

Colorless diamonds can command high prices as gemstones. A type of less valuable diamonds can be treated to remove all color. Only sophisticated tests can distinguish such treated diamonds from naturally colorless ones. 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. Surely, therefore, the vast majority of colorless diamonds sold by jewelers are naturally colorless.

A serious flaw in the reasoning of the argument is that

comparisons between the price diamonds command as gemstones and their value for other uses are omitted

information about the rarity of treated diamonds is not combined with information about the rarity of naturally colorless, gemstone diamonds

the possibility that colored diamonds might be used as gemstones, even without having been treated, is ignored

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

the difficulty that a customer of a jeweler would have in distinguishing a naturally colorless diamond from treated one is not taken into account

Solution

Passage Analysis:

Text from Passage	Analysis
Colorless diamonds can command high prices as gemstones.	What it says: Colorless diamonds are valuable and sell for high prices What it does: Sets up the basic premise about diamond value What it is: Background fact
A type of less valuable diamonds can be treated to remove all color.	What it says: Some cheaper diamonds can be made colorless through treatment What it does: Introduces the key concept that connects cheaper diamonds to valuable ones What it is: Technical fact Visualization: Less valuable diamonds → Treatment process → Colorless appearance (mimics naturally colorless diamonds)
Only sophisticated tests can distinguish such treated diamonds from naturally colorless ones.	What it says: Treated and natural colorless diamonds look identical to regular inspection What it does: Shows why treated diamonds could potentially fool buyers in the market What it is: Technical limitation
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.	What it says: Very few diamonds (2%) can even be treated, and many of those aren't worth treating What it does: Provides numerical evidence to limit how many treated diamonds could exist What it is: Statistical evidence Visualization: 100 diamonds mined → 2 can be treated → Even fewer (maybe 1) are actually worth treating
Surely, therefore, the vast majority of colorless diamonds sold by jewelers are naturally colorless.	What it says: Most colorless diamonds in jewelry stores must be natural, not treated What it does: Draws the main conclusion based on the 2% limitation argument What it is: Author's conclusion

Argument Flow:

The argument starts by establishing that colorless diamonds are valuable, then introduces the possibility that treated diamonds could flood the market since they're undetectable. However, it pivots to show that very few diamonds can even be treated (only 2%), and many of those aren't worth treating, leading to the conclusion that most colorless diamonds must be natural.

Main Conclusion:

The vast majority of colorless diamonds sold by jewelers are naturally colorless (not treated ones).

Logical Structure:

The author uses a quantity-based argument: since only 2% of diamonds can be treated and many of those aren't worth treating, there simply aren't enough treated diamonds to make up a significant portion of the colorless diamond market. However, this reasoning has a serious flaw - it only considers the supply of treatable diamonds from mining, but doesn't account for what percentage of the colorless diamond market those few treated diamonds might actually represent.

Prethinking:

Question type:

Misc (Flaw) - We need to identify a serious logical error in the argument's reasoning that undermines the conclusion

Precision of Claims

The argument makes quantity-based claims (2% of diamonds can be treated, vast majority are natural) and activity-based claims (mining, treating, selling)

Strategy

Look for gaps between what the argument establishes and what it concludes. The author concludes that most colorless diamonds sold are natural based on the low percentage that can be treated, but we need to find what critical assumption or logical step is missing or flawed

Answer Choices Explained

comparisons between the price diamonds command as gemstones and their value for other uses are omitted

This isn't relevant to the argument's flaw. The argument isn't trying to compare different uses of diamonds; it's trying to determine the composition of the colorless diamond market. The omission of price comparisons for different uses doesn't undermine the logic about market composition.

information about the rarity of treated diamonds is not combined with information about the rarity of naturally colorless, gemstone diamonds

This correctly identifies the critical flaw. We know that only 2% of diamonds can be treated, but we have no information about how rare naturally colorless diamonds are. If natural colorless diamonds are extremely rare (maybe 0.5% of diamonds mined), then even the small supply of treated diamonds could outnumber them in jewelry stores. The argument's conclusion falls apart without this crucial comparison.

the possibility that colored diamonds might be used as gemstones, even without having been treated, is ignored

This doesn't address the argument's logic about colorless diamonds. The argument is specifically about the composition of the colorless diamond market, not about whether colored diamonds can also be used as gemstones. This omission doesn't create a flaw in the reasoning about colorless diamonds.

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

The argument doesn't make any claims about this being the only method or worry about future methods. It's analyzing the current market situation based on current capabilities. Even if there were multiple methods, the 2% limitation would still apply to the raw material.

the difficulty that a customer of a jeweler would have in distinguishing a naturally colorless diamond from treated one is not taken into account

Actually, this is mentioned in the argument ('Only sophisticated tests can distinguish such treated diamonds from naturally colorless ones'). More importantly, customer difficulty in distinguishing doesn't affect the logical flaw about market composition - it's about supply ratios, not detection ability.

Rate this Solution

Tell us what you think about this solution

...

Forum Discussions

Start a new discussion

Post

Previous Attempts

Loading attempts...