GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 16 Jun 2019, 23:57

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# The determination of the sources of copper ore used i

Author Message
TAGS:

### Hide Tags

Board of Directors
Joined: 01 Sep 2010
Posts: 3360
The determination of the sources of copper ore used i  [#permalink]

### Show Tags

27 Jun 2018, 13:41
1
Top Contributor
Question 1
00:00

based on 207 sessions

76% (03:12) correct 24% (03:20) wrong

### HideShow timer Statistics

Question 2
00:00

based on 215 sessions

92% (00:47) correct 8% (00:51) wrong

### HideShow timer Statistics

Question 3
00:00

based on 204 sessions

30% (01:24) correct 70% (01:37) wrong

### HideShow timer Statistics

Question 4
00:00

based on 197 sessions

66% (01:08) correct 34% (01:20) wrong

### HideShow timer Statistics

Question 5
00:00

based on 198 sessions

60% (01:08) correct 40% (01:05) wrong

### HideShow timer Statistics

Question 6
00:00

based on 190 sessions

89% (00:54) correct 11% (00:47) wrong

### HideShow timer Statistics

Question 7
00:00

based on 182 sessions

40% (01:30) correct 60% (01:54) wrong

### HideShow timer Statistics

The determination of the sources of copper ore used in the manufacture of copper and bronze artifacts of Bronze Age civilizations would add greatly to our knowledge of cultural contacts and trade in that era. Researchers have analyzed artifacts and ores for their concentrations of elements, but for a variety of reasons. these studies have generally failed to provide evidence of the sources of the copper used in the objects. Elemental composition can vary within the same copper-ore lode, usually because of varying admixtures of other elements, especially iron, lead, zinc, and arsenic. And high concentrations of cobalt or zinc, noticed in some artifacts, appear in a variety of copper-ore sources. Moreover, the processing of ores introduced poorly controlled changes in the concentrations of minor and trace elements in the resulting metal. Some elements evaporate during smelting and roasting: different temperatures and processes produce different degrees of loss. Finally, flux, which is sometimes added during smelting to remove waste material from the ore, could add quantities of elements to the final product.

An elemental property that is unchanged through these chemical processes is the isotopic composition of each metallic element in the ore. Isotopic composition. the percentages of the different isotopes of an element in a given sample of the element, is therefore particularly suitable as an indicator of the sources of the ore. Of course, for this purpose, it is necessary to find an element whose isotopic composition is more or less constant throughout a given ore body but varies from one copper ore body to another or, at least, from one geographic region to another.

The ideal choice, when the isotopic composition is used to investigate the source of copper ore, would seem to be copper itself. It has been shown that small but measurable variations occur naturally in the isotopic composition of copper. However, the variations are large enough only in rare ores; between samples of the common ore minerals of copper, isotopic variations greater than the measurement error have not been found. An alternative choice is lead, which occurs in most copper and bronze artifacts of the Bronze Age in amounts consistent with the lead being derived from the copper ores and possibly from the fluxes. The isotopic composition of lead often varies from one source of common copper ore to another, with variations exceeding the measurement error; and preliminary studies indicate virtually uniform isotopic composition of the lead from a single copper-ore source. While some of the lead found in an artifact may have been introduced from flux or when other metals were added to the copper ore, lead so added in Bronze Age processing would usually have the same isotopic composition as the lead in the copper ore. Lead isotope studies may thus prove useful for interpreting the archaeological record of the Bronze Age.
1) The primary purpose of the passage is to

(A) discuss the techniques of analyzing lead isotope composition
(B) propose a way to determine the origin of the copper in certain artifacts
(C) resolve a dispute concerning the analysis of copper ore
(D) describe the deficiencies of a currently used method of chemical analysis of certain metals
(E) offer an interpretation of the archaeological record of the Bronze Age

Spoiler: :: OA
B

2) The author first mentions the addition of flux during smelting in order to

(A) give a reason for the failure of elemental composition studies to determine ore sources
(B) illustrate differences between various Bronze Age civilizations
(C) show the need for using high smelting temperatures
(D) illustrate the uniformity of lead isotope composition
(E) explain the success of copper isotope composition analysis

Spoiler: :: OA
A

3) The author suggests which of the following about a Bronze Age artifact containing high concentrations of cobalt or zinc?

(A) It could not be reliably tested for its elemental composition.
(B) It could not be reliably tested for its copper isotope composition.
(C) It could not be reliably tested for its lead isotope composition.
(D) It could have been manufactured from ore from any one of a variety of sources.
(E) It could have been produced by the addition of other metals during the processing of the copper ore.

Spoiler: :: OA
D

4) According to the passage, possible sources of the lead found in a copper or bronze artifact include which of the following?

I. The copper ore used to manufacture the artifact
II. Flux added during processing of the copper ore
III. Other metal added during processing of the copper ore

(A) I only
(B) II only
(C) III only
(D) II and III only
(E) I, II, and III

Spoiler: :: OA
E

5) The author rejects copper as the "ideal choice" mentioned because

(A) the concentration of copper in Bronze Age artifacts varies
(B) elements other than copper may be introduced during smelting
(C) the isotopic composition of copper changes during smelting
(D) among common copper ores, differences in copper isotope composition are too small
(E) within a single source of copper ore, copper isotope composition can vary substantially

Spoiler: :: OA
D

6) The author makes which of the following statements about lead isotope composition?

(A) It often varies from one copper-ore source to another.
(B) It sometimes varies over short distances in a single copper-ore source.
(C) It can vary during the testing of artifacts, producing a measurement error.
(D) It frequently changes during smelting and roasting.
(E) It may change when artifacts are buried for thousands of years.

Spoiler: :: OA
A

7) It can be inferred from the passage that the use of flux in processing copper ore can alter the lead isotope composition of the resulting metal EXCEPT when

(A) there is a smaller concentration of lead in the flux than in the copper ore
(B) the concentration of lead in the flux is equivalent to that of the lead in the ore
(C) some of the lead in the flux evaporates during processing
(D) any lead in the flux has the same isotopic composition as the lead in the ore
(E) other metals are added during processing

Spoiler: :: OA
D

NOTE: passage from official GRE Material.

_________________
Manager
Joined: 06 Mar 2018
Posts: 59
Location: India
GRE 1: Q160 V150
GPA: 2.7
Re: The determination of the sources of copper ore used i  [#permalink]

### Show Tags

28 Jun 2018, 07:18
In Que 4 , I don't understand how E can be the answer. I can only figure out II and III. I don't understand where "The copper ore used to manufacture the artifact" is given in the passage.
Intern
Joined: 17 Apr 2018
Posts: 3
Re: The determination of the sources of copper ore used i  [#permalink]

### Show Tags

28 Jun 2018, 10:25
carcass wrote:
The determination of the sources of copper ore used in the manufacture of copper and bronze artifacts of Bronze Age civilizations would add greatly to our knowledge of cultural contacts and trade in that era. Researchers have analyzed artifacts and ores for their concentrations of elements, but for a variety of reasons. these studies have generally failed to provide evidence of the sources of the copper used in the objects. Elemental composition can vary within the same copper-ore lode, usually because of varying admixtures of other elements, especially iron, lead, zinc, and arsenic. And high concentrations of cobalt or zinc, noticed in some artifacts, appear in a variety of copper-ore sources. Moreover, the processing of ores introduced poorly controlled changes in the concentrations of minor and trace elements in the resulting metal. Some elements evaporate during smelting and roasting: different temperatures and processes produce different degrees of loss. Finally, flux, which is sometimes added during smelting to remove waste material from the ore, could add quantities of elements to the final product.

An elemental property that is unchanged through these chemical processes is the isotopic composition of each metallic element in the ore. Isotopic composition. the percentages of the different isotopes of an element in a given sample of the element, is therefore particularly suitable as an indicator of the sources of the ore. Of course, for this purpose, it is necessary to find an element whose isotopic composition is more or less constant throughout a given ore body but varies from one copper ore body to another or, at least, from one geographic region to another.

The ideal choice, when the isotopic composition is used to investigate the source of copper ore, would seem to be copper itself. It has been shown that small but measurable variations occur naturally in the isotopic composition of copper. However, the variations are large enough only in rare ores; between samples of the common ore minerals of copper, isotopic variations greater than the measurement error have not been found. An alternative choice is lead, which occurs in most copper and bronze artifacts of the Bronze Age in amounts consistent with the lead being derived from the copper ores and possibly from the fluxes. The isotopic composition of lead often varies from one source of common copper ore to another, with variations exceeding the measurement error; and preliminary studies indicate virtually uniform isotopic composition of the lead from a single copper-ore source. While some of the lead found in an artifact may have been introduced from flux or when other metals were added to the copper ore, lead so added in Bronze Age processing would usually have the same isotopic composition as the lead in the copper ore. Lead isotope studies may thus prove useful for interpreting the archaeological record of the Bronze Age.
1) The primary purpose of the passage is to

(A) discuss the techniques of analyzing lead isotope composition
(B) propose a way to determine the origin of the copper in certain artifacts
(C) resolve a dispute concerning the analysis of copper ore
(D) describe the deficiencies of a currently used method of chemical analysis of certain metals
(E) offer an interpretation of the archaeological record of the Bronze Age

Spoiler: :: OA
B

2) The author first mentions the addition of flux during smelting in order to

(A) give a reason for the failure of elemental composition studies to determine ore sources
(B) illustrate differences between various Bronze Age civilizations
(C) show the need for using high smelting temperatures
(D) illustrate the uniformity of lead isotope composition
(E) explain the success of copper isotope composition analysis

Spoiler: :: OA
A

3) The author suggests which of the following about a Bronze Age artifact containing high concentrations of cobalt or zinc?

(A) It could not be reliably tested for its elemental composition.
(B) It could not be reliably tested for its copper isotope composition.
(C) It could not be reliably tested for its lead isotope composition.
(D) It could have been manufactured from ore from any one of a variety of sources.
(E) It could have been produced by the addition of other metals during the processing of the copper ore.

Spoiler: :: OA
D

4) According to the passage, possible sources of the lead found in a copper or bronze artifact include which of the following?

I. The copper ore used to manufacture the artifact
II. Flux added during processing of the copper ore
III. Other metal added during processing of the copper ore

(A) I only
(B) II only
(C) III only
(D) II and III only
(E) I, II, and III

Spoiler: :: OA
E

5) The author rejects copper as the "ideal choice" mentioned because

(A) the concentration of copper in Bronze Age artifacts varies
(B) elements other than copper may be introduced during smelting
(C) the isotopic composition of copper changes during smelting
(D) among common copper ores, differences in copper isotope composition are too small
(E) within a single source of copper ore, copper isotope composition can vary substantially

Spoiler: :: OA
D

6) The author makes which of the following statements about lead isotope composition?

(A) It often varies from one copper-ore source to another.
(B) It sometimes varies over short distances in a single copper-ore source.
(C) It can vary during the testing of artifacts, producing a measurement error.
(D) It frequently changes during smelting and roasting.
(E) It may change when artifacts are buried for thousands of years.

Spoiler: :: OA
A

7) It can be inferred from the passage that the use of flux in processing copper ore can alter the lead isotope composition of the resulting metal EXCEPT when

(A) there is a smaller concentration of lead in the flux than in the copper ore
(B) the concentration of lead in the flux is equivalent to that of the lead in the ore
(C) some of the lead in the flux evaporates during processing
(D) any lead in the flux has the same isotopic composition as the lead in the ore
(E) other metals are added during processing

Spoiler: :: OA
D

Can someone explain how D is the solution for ques 7?
Intern
Joined: 17 Feb 2018
Posts: 2
Re: The determination of the sources of copper ore used i  [#permalink]

### Show Tags

28 Jun 2018, 12:23
AnkitRajSrivastava wrote:

Can someone explain how D is the solution for ques 7?

Hi Ankit,
It's said that "While some of the lead found in an artifact may have been introduced from flux or when other metals were added to the copper ore, lead so added in Bronze Age processing would usually have the same isotopic composition as the lead in the copper ore," and then the passage concluded "Lead isotope studies may thus prove useful for interpreting the archaeological record of the Bronze Age."
We can understand that even though lead were added from the flux used in processing the artifacts, if these lead have the same isotopic composition as the lead in the copper ore, the result of the isotopic analysis is still reliable. In another word, the flux didn't change the lead isotope composition of the resulting metal.
Intern
Joined: 17 Feb 2018
Posts: 2
Re: The determination of the sources of copper ore used i  [#permalink]

### Show Tags

28 Jun 2018, 12:29
prags1989 wrote:
In Que 4 , I don't understand how E can be the answer. I can only figure out II and III. I don't understand where "The copper ore used to manufacture the artifact" is given in the passage.

You can find that information in these sentences from the last paragraph: "An alternative choice is lead, which occurs in most copper and bronze artifacts of the Bronze Age in amounts consistent with the lead being derived from the copper ores and possibly from the fluxes. The isotopic composition of lead often varies from one source of common copper ore to another..."
If the isotopic composition of lead varies from one source of copper ore to another, and we know the isotopic composition of lead found in the artifact, we can determine the ore where the lead is from.
CR Forum Moderator
Joined: 25 Apr 2018
Posts: 570
Re: The determination of the sources of copper ore used i  [#permalink]

### Show Tags

06 Aug 2018, 03:48
Hi carcass

Can you please tell what is the source of this passage?

Thanks!
_________________

Project CR Butler - 2 CR's everyday
Board of Directors
Joined: 01 Sep 2010
Posts: 3360
Re: The determination of the sources of copper ore used i  [#permalink]

### Show Tags

09 Jan 2019, 02:31
Top Contributor
Hi,

it is an Official passage from the GRE test.

Regards
_________________
MBA Section Director
Affiliations: GMATClub
Joined: 22 May 2017
Posts: 2526
GPA: 4
WE: Engineering (Computer Software)
Re: The determination of the sources of copper ore used i  [#permalink]

### Show Tags

13 Jan 2019, 21:12

+1 kudos to the posts containing answer explanations of all questions

_________________
Senior PS Moderator
Status: It always seems impossible until it's done.
Joined: 16 Sep 2016
Posts: 750
GMAT 1: 740 Q50 V40
GMAT 2: 770 Q51 V42
Re: The determination of the sources of copper ore used i  [#permalink]

### Show Tags

14 Jan 2019, 23:00
1

The passage starts with why it is important to determine the sources of copper found in bronze age artifacts. Goes on to detail a problem with doing so, how studies up until that point have failed due to various reasons such as poor process back in the day which added many impurities. The author reveals that even though we can identify what all elements & their concentrations are present it becomes impossible to identify the source of copper ore. The author then introduces a new plausible technique of ""composition of isotopes of metals" to possibly determine the ore source but goes on to convey that an element with constant isotopic concentration is needed. The first choice is of copper but differences in isotopic variations of "common copper ore sources" are not high enough for measurement so copper is discarded. Finally, the author settles with lead, whose isotopic variations are constant at common sources of ores and are high enough to be measured. So lead will lead the way

1) The primary purpose of the passage is to
(A) discuss the techniques of analyzing lead isotope composition too detailed to be primary purpose
(B) propose a way to determine the origin of the copper in certain artifacts Perfect - the author ends with this note stating that lead isotopic composition is a way to determine origin of copper
(C) resolve a dispute concerning the analysis of copper ore there is no dispute
(D) describe the deficiencies of a currently used method of chemical analysis of certain metals TRAP - this is done but this is not the primary purpose, the first paragraph is used only to set up the scene
(E) offer an interpretation of the archaeological record of the Bronze Age Not quite right, we are looking to identify the sources of copper and not offer an iterpretation. What we offer is more tangible than just an interpretation

Mentioned in the first paragraphs when we are listing the shortcomings of the traditional approach to identifying sources of copper
2) The author first mentions the addition of flux during smelting in order to
(A) give a reason for the failure of elemental composition studies to determine ore sources Perfect - need to realize the context with which the author is mentioning - turn on your critical reasoning brain
(B) illustrate differences between various Bronze Age civilizations Not quite true - just the sources of copper are what we are interested in
(C) show the need for using high smelting temperatures Opposite - this is true but not why the author states this
(D) illustrate the uniformity of lead isotope composition lead isotope is not mentioned here
(E) explain the success of copper isotope composition analysis 180 opposite choice - it is related to the failure and not a success

Straightforward detail question
3) The author suggests which of the following about a Bronze Age artifact containing high concentrations of cobalt or zinc?
(A) It could not be reliably tested for its elemental composition. It has been identified with Cobalt and zinc - so this option is self contradictory
(B) It could not be reliably tested for its copper isotope composition. Not true as per passage
(C) It could not be reliably tested for its lead isotope composition. Not true as per passage
(D) It could have been manufactured from ore from any one of a variety of sources. Perfect - this is verbatim from the passage
(E) It could have been produced by the addition of other metals during the processing of the copper ore. TRAP - a play of words - remember we are talking about artifact here.

Super easydetail question
4) According to the passage, possible sources of the lead found in a copper or bronze artifact include which of the following?
I. The copper ore used to manufacture the artifact CORRECT
II. Flux added during processing of the copper ore CORRECT
III. Other metal added during processing of the copper ore CORRECT

(A) I only
(B) II only
(C) III only
(D) II and III only
(E) I, II, and III Tick

This is the main point on which the argument of the author in the third paragraph is based - copper is not a good choice even if it was our first choice.
5) The author rejects copper as the "ideal choice" mentioned because
(A) the concentration of copper in Bronze Age artifacts varies Opposite - this could be why it would be a good choice.
(B) elements other than copper may be introduced during smelting Irrelevant as we are talking about isotopic study
(C) the isotopic composition of copper changes during smelting TRAP - could be a likely choice if it were true but this is not true as per what the author mentions in the second paragraph
(D) among common copper ores, differences in copper isotope composition are too small Perfect - exactly what we are looking for - verbatim from the passage
(E) within a single source of copper ore, copper isotope composition can vary substantially If this were true than it would go against - hence this is a trap choice. However, it is not true but this is not why copper is bad - we just cannot measure it that is why it is bad.

6) The author makes which of the following statements about lead isotope composition?
(A) It often varies from one copper-ore source to another. Perfect - and that is why we can use it as a marker to find out the source of copper ore
(B) It sometimes varies over short distances in a single copper-ore source. Not mentioned and would go against the main conclusion of the passage - lead is a good choice.
(C) It can vary during the testing of artifacts, producing a measurement error. Wrong for same reason as above.
(D) It frequently changes during smelting and roasting. Same as above
(E) It may change when artifacts are buried for thousands of years. Nonsensical option. discard.

Twisted detail question but one that is mentioned in the finishing lines of the passage
7) It can be inferred from the passage that the use of flux in processing copper ore can alter the lead isotope composition of the resulting metal EXCEPT when
(A) there is a smaller concentration of lead in the flux than in the copper ore TRAP - real-world trap - could be true but not mentioned
(B) the concentration of lead in the flux is equivalent to that of the lead in the ore TRAP - something is equivalent but not the concentration of lead - it is the isotope that we are lookingfor
(C) some of the lead in the flux evaporates during processing Irrelevant to the question
(D) any lead in the flux has the same isotopic composition as the lead in the ore Perfect - this has been mentioned in the passage as a reason why lead isotope method is reliable
(E) other metals are added during processing Again irrelevant

Hope my comments are useful to you.
_________________
Regards,

“Do. Or do not. There is no try.” - Yoda (The Empire Strikes Back)
Manager
Joined: 04 Jun 2018
Posts: 157
GMAT 1: 610 Q48 V25
GMAT 2: 690 Q50 V32
GMAT 3: 710 Q50 V36
Re: The determination of the sources of copper ore used i  [#permalink]

### Show Tags

15 Jan 2019, 00:38

The passage starts with why it is important to determine the sources of copper found in bronze age artifacts. Goes on to detail a problem with doing so, how studies up until that point have failed due to various reasons such as poor process back in the day which added many impurities. The author reveals that even though we can identify what all elements & their concentrations are present it becomes impossible to identify the source of copper ore. The author then introduces a new plausible technique of ""composition of isotopes of metals" to possibly determine the ore source but goes on to convey that an element with constant isotopic concentration is needed. The first choice is of copper but differences in isotopic variations of "common copper ore sources" are not high enough for measurement so copper is discarded. Finally, the author settles with lead, whose isotopic variations are constant at common sources of ores and are high enough to be measured. So lead will lead the way

1) The primary purpose of the passage is to
(A) discuss the techniques of analyzing lead isotope composition too detailed to be primary purpose
(B) propose a way to determine the origin of the copper in certain artifacts Perfect - the author ends with this note stating that lead isotopic composition is a way to determine origin of copper
(C) resolve a dispute concerning the analysis of copper ore there is no dispute
(D) describe the deficiencies of a currently used method of chemical analysis of certain metals TRAP - this is done but this is not the primary purpose, the first paragraph is used only to set up the scene
(E) offer an interpretation of the archaeological record of the Bronze Age Not quite right, we are looking to identify the sources of copper and not offer an iterpretation. What we offer is more tangible than just an interpretation

Mentioned in the first paragraphs when we are listing the shortcomings of the traditional approach to identifying sources of copper
2) The author first mentions the addition of flux during smelting in order to
(A) give a reason for the failure of elemental composition studies to determine ore sources Perfect - need to realize the context with which the author is mentioning - turn on your critical reasoning brain
(B) illustrate differences between various Bronze Age civilizations Not quite true - just the sources of copper are what we are interested in
(C) show the need for using high smelting temperatures Opposite - this is true but not why the author states this
(D) illustrate the uniformity of lead isotope composition lead isotope is not mentioned here
(E) explain the success of copper isotope composition analysis 180 opposite choice - it is related to the failure and not a success

Straightforward detail question
3) The author suggests which of the following about a Bronze Age artifact containing high concentrations of cobalt or zinc?
(A) It could not be reliably tested for its elemental composition. It has been identified with Cobalt and zinc - so this option is self contradictory
(B) It could not be reliably tested for its copper isotope composition. Not true as per passage
(C) It could not be reliably tested for its lead isotope composition. Not true as per passage
(D) It could have been manufactured from ore from any one of a variety of sources. Perfect - this is verbatim from the passage
(E) It could have been produced by the addition of other metals during the processing of the copper ore. TRAP - a play of words - remember we are talking about artifact here.

Super easydetail question
4) According to the passage, possible sources of the lead found in a copper or bronze artifact include which of the following?
I. The copper ore used to manufacture the artifact CORRECT
II. Flux added during processing of the copper ore CORRECT
III. Other metal added during processing of the copper ore CORRECT

(A) I only
(B) II only
(C) III only
(D) II and III only
(E) I, II, and III Tick

This is the main point on which the argument of the author in the third paragraph is based - copper is not a good choice even if it was our first choice.
5) The author rejects copper as the "ideal choice" mentioned because
(A) the concentration of copper in Bronze Age artifacts varies Opposite - this could be why it would be a good choice.
(B) elements other than copper may be introduced during smelting Irrelevant as we are talking about isotopic study
(C) the isotopic composition of copper changes during smelting TRAP - could be a likely choice if it were true but this is not true as per what the author mentions in the second paragraph
(D) among common copper ores, differences in copper isotope composition are too small Perfect - exactly what we are looking for - verbatim from the passage
(E) within a single source of copper ore, copper isotope composition can vary substantially If this were true than it would go against - hence this is a trap choice. However, it is not true but this is not why copper is bad - we just cannot measure it that is why it is bad.

6) The author makes which of the following statements about lead isotope composition?
(A) It often varies from one copper-ore source to another. Perfect - and that is why we can use it as a marker to find out the source of copper ore
(B) It sometimes varies over short distances in a single copper-ore source. Not mentioned and would go against the main conclusion of the passage - lead is a good choice.
(C) It can vary during the testing of artifacts, producing a measurement error. Wrong for same reason as above.
(D) It frequently changes during smelting and roasting. Same as above
(E) It may change when artifacts are buried for thousands of years. Nonsensical option. discard.

Twisted detail question but one that is mentioned in the finishing lines of the passage
7) It can be inferred from the passage that the use of flux in processing copper ore can alter the lead isotope composition of the resulting metal EXCEPT when
(A) there is a smaller concentration of lead in the flux than in the copper ore TRAP - real-world trap - could be true but not mentioned
(B) the concentration of lead in the flux is equivalent to that of the lead in the ore TRAP - something is equivalent but not the concentration of lead - it is the isotope that we are lookingfor
(C) some of the lead in the flux evaporates during processing Irrelevant to the question
(D) any lead in the flux has the same isotopic composition as the lead in the ore Perfect - this has been mentioned in the passage as a reason why lead isotope method is reliable
(E) other metals are added during processing Again irrelevant

Hope my comments are useful to you.

Great explaination
Great efficiency too
6min WOW!

Now I am a very slow reader, SO it took a significantly higher time.
Nevertheless, I have a doubt in q3.

This is a part of the first passage. Can you tell me why is this portion stated where it has been stated. And what does this exactly mean?
Also Can you provide a reasoning for why Option D for question 3 is the right answer?

Elemental composition can vary within the same copper-ore lode, usually because of varying admixtures of other elements, especially iron, lead, zinc, and arsenic. And high concentrations of cobalt or zinc, noticed in some artifacts, appear in a variety of copper-ore sources. Moreover, the processing of ores introduced poorly controlled changes in the concentrations of minor and trace elements in the resulting metal.

Regards
Nitesh
Senior PS Moderator
Status: It always seems impossible until it's done.
Joined: 16 Sep 2016
Posts: 750
GMAT 1: 740 Q50 V40
GMAT 2: 770 Q51 V42
Re: The determination of the sources of copper ore used i  [#permalink]

### Show Tags

15 Jan 2019, 01:05
Thanks for the praise

So for Q3 - cobalt and zinc - check out line 10 of the passage -"And high concentrations of cobalt or zinc, noticed in some artifacts, appear in a variety of copper-ore sources." I think in the context of the passage the author is trying to find markers ( either elements or isotopes of elements) that can reveal the exact source of copper ore which was used to create the artifact and hence find out more about trade & other insights into Bronze age.

So, when the author mentions that when copper with cobalt and zinc high concentrations is found in some artifacts but such copper type appear in various copper ore sources it becomes clear that cobalt and zinc cannot be used to uniquely identify the source. Hence Option (D) fits well.

nitesh50 wrote:

Great explaination
Great efficiency too
6min WOW!

Now I am a very slow reader, SO it took a significantly higher time.
Nevertheless, I have a doubt in q3.

This is a part of the first passage. Can you tell me why is this portion stated where it has been stated. And what does this exactly mean?
Also Can you provide a reasoning for why Option D for question 3 is the right answer?

Elemental composition can vary within the same copper-ore lode, usually because of varying admixtures of other elements, especially iron, lead, zinc, and arsenic. And high concentrations of cobalt or zinc, noticed in some artifacts, appear in a variety of copper-ore sources. Moreover, the processing of ores introduced poorly controlled changes in the concentrations of minor and trace elements in the resulting metal.

Regards
Nitesh

_________________
Regards,

“Do. Or do not. There is no try.” - Yoda (The Empire Strikes Back)
Manager
Joined: 04 Jun 2018
Posts: 157
GMAT 1: 610 Q48 V25
GMAT 2: 690 Q50 V32
GMAT 3: 710 Q50 V36
Re: The determination of the sources of copper ore used i  [#permalink]

### Show Tags

15 Jan 2019, 01:35
Thanks for the praise

So for Q3 - cobalt and zinc - check out line 10 of the passage -"And high concentrations of cobalt or zinc, noticed in some artifacts, appear in a variety of copper-ore sources." I think in the context of the passage the author is trying to find markers ( either elements or isotopes of elements) that can reveal the exact source of copper ore which was used to create the artifact and hence find out more about trade & other insights into Bronze age.

So, when the author mentions that when copper with cobalt and zinc high concentrations is found in some artifacts but such copper type appear in various copper ore sources it becomes clear that cobalt and zinc cannot be used to uniquely identify the source. Hence Option (D) fits well.

nitesh50 wrote:

Great explaination
Great efficiency too
6min WOW!

Now I am a very slow reader, SO it took a significantly higher time.
Nevertheless, I have a doubt in q3.

This is a part of the first passage. Can you tell me why is this portion stated where it has been stated. And what does this exactly mean?
Also Can you provide a reasoning for why Option D for question 3 is the right answer?

Elemental composition can vary within the same copper-ore lode, usually because of varying admixtures of other elements, especially iron, lead, zinc, and arsenic. And high concentrations of cobalt or zinc, noticed in some artifacts, appear in a variety of copper-ore sources. Moreover, the processing of ores introduced poorly controlled changes in the concentrations of minor and trace elements in the resulting metal.

Regards
Nitesh

I still don't get it. Geography and minerals were never my good friends. So we don't get along much.
SO I will try explaining to you the part where I am having problems in.
Perhaps you can figure my problem out.

Elemental composition can vary within the same copper-ore lode, usually because of varying admixtures of other elements, especially iron, lead, zinc, and arsenic.

SO the author in the previous sentence said that the studies were unsuccessful in identifying the sources of copper. SO this might be the reason for the difficulty.
The elemental composition i.e the elements in the copper ore vary because of the different mixtures of other materials.

Question still unanswered: How does elemental composition create a problem?

And high concentrations of cobalt or zinc, noticed in some artifacts, appear in a variety of copper-ore sources.

Another type of minerals: Cobalt and zinc appear in high concentrations in artifacts. so the elemental composition may also have cobalt or zinc.

Option D: artifacts could have been manufactured from ore from any one of a variety of sources.
Now how does the author derive this statement?

I feel IMO Option A makes slightly more sense:
A) It could not be reliably tested for its elemental composition.

Since there were so may elements, testing it for elemental composition became difficult.

Regards
Senior PS Moderator
Status: It always seems impossible until it's done.
Joined: 16 Sep 2016
Posts: 750
GMAT 1: 740 Q50 V40
GMAT 2: 770 Q51 V42
Re: The determination of the sources of copper ore used i  [#permalink]

### Show Tags

15 Jan 2019, 01:46
1
Please find my detailed respones in-line. This should clear all your doubts.

nitesh50 wrote:

I still don't get it. Geography and minerals were never my good friends. So we don't get along much. I am in the same category - however, here I feel one just needs to employ reasoning skills as everything else feels logical
SO I will try explaining to you the part where I am having problems in.
Perhaps you can figure my problem out.

Elemental composition can vary within the same copper-ore lode, usually because of varying admixtures of other elements, especially iron, lead, zinc, and arsenic.

SO the author in the previous sentence said that the studies were unsuccessful in identifying the sources of copper. SO this might be the reason for the difficulty.
The elemental composition i.e the elements in the copper ore vary because of the different mixtures of other materials. The elements vary in the ore but this is just a fact - this does not entail a causal relationship like you pointed out in the part which I struck-through

Question still unanswered: How does elemental composition create a problem? This I feel is more of a main point thing - the main idea of the passage is linking "source of copper" to artifacts. and not finding elemental composition or anything else... those are just the means to the end

And high concentrations of cobalt or zinc, noticed in some artifacts, appear in a variety of copper-ore sources.

Another type of minerals: Cobalt and zinc appear in high concentrations in artifacts. so the elemental composition may also have cobalt or zinc. Perfectly captured but you missed the crux of what the author wanted to convey - which I pointed out in my previous post let me do it again - "Since high conc of cobalt & zinc -> variety of ore sources .. therefore, we cannot link an artifact with high conc of cobalt & zinc to a particular source... it could be from any of the various possibilities"

Option D: artifacts could have been manufactured from ore from any one of a variety of sources.
Now how does the author derive this statement? That is how... read my comments above - it is pretty clear. No debates to this OA.

I feel IMO Option A makes slightly more sense:
A) It could not be reliably tested for its elemental composition. Again - you are falling for the traps - the artifact can definitely be tested for elemental composition but the elemental composition cannot be reliably used to detect the source of copper ore

Think on these lines - in the context of getting a blood report from a doctor to test for malaria. Not being able to get a blood report is not the same as not being able to ascertain if you have malaria or not from a blood report.

Since there were so may elements, testing it for elemental composition became difficult.

Regards

_________________
Regards,

“Do. Or do not. There is no try.” - Yoda (The Empire Strikes Back)
Re: The determination of the sources of copper ore used i   [#permalink] 15 Jan 2019, 01:46
Display posts from previous: Sort by