Gold is typically mined from two different types of geologic formation

Question

Gold is typically mined from two different types of geologic formations (known as deposits): lode deposits and placer deposits. Lode deposits are what prospectors dream of finding: large deposits of nearly pure gold. Such deposits are located where they were originally deposited by the mineral-bearing solutions that carried the gold up from the earth’s interior. Placer deposits, on the other hand, come from preexisting lode deposits that are exposed at the surface of the earth. These lode deposits’ exposure to the weather causes gold to be released from the surrounding rock and transported by rivers in the form of dust or flakes. When a stream carrying the gold slows, the gold collects in pockets of sand. Placer-deposit mines have historically been the source of approximately 35 percent of the total gold mined in the US. However, in recent years, the quantity of gold mined from such deposits has decreased as the readily accessible deposits have been exhausted. Thus, despite an increase in net gold mined, placer-deposit mining now accounts for only a few percent of total gold mined in the US.

Mining lode deposits has a much larger environmental impact by virtue of the size of such operations, the generation of waste material, and the use of toxic chemicals. The gold comes out of the ground as raw ore—gold aggregated with other minerals. On average, such mining operations process approximately 130 kilograms of raw ore to produce 1 gram of pure gold. Unlike placer-deposit mines, modern commercial lode-deposit mines are massive operations, some displacing and processing up to 180,000 metric tons (1 metric ton = 1,000 kilograms) of raw ore per day.

Apt0810 · Accepted Answer

1)a)Implied,since it's written that is the largest gold mine in the world so it would be going through lode deposits,which requires chemicals for gold extraction.
b)Not implied,since it is not pointing towards placer deposit rather it's a lode deposit
c)Not implied,since it is not pointing towards placer deposit rather it's a lode deposit

2)a)Not justified,since lode deposits are located beneath the earth and gold comes from earth's interior
b)Not justified,since lode can't be created by placers since loses are found beneath the earth
c)justified,since placer are transported by rivers and are in form of dust and lakes so they are located within the paths of former or current rivers

3)D,since we know per the passage that habitat destruction and sediment release are the principal forms of damage attributed to placer deposits

4)a)No,since placer would be lesser than lodes since placers are formed through lodes
b)Yes,it may happen since habitat destruction and sediment release are primary effects so other effects might also be there
c)No, it's not the Increased quantity but the ease of access with the lode deposits which make their extraction possible.

5)a)Not supported,since the scientist just quote the above point without any specific evidence to show the validity of this point.
b)Not supported,since the scientist just quote the above point without any specific evidence to show the validity of this point.
c) Supported,since scientist qoutes the evidence :"Unlike placer-deposit mines, modern commercial lode-deposit mines are massive operations, some displacing and processing up to 180,000 metric tons (1 metric ton = 1,000 kilograms) of raw ore per day."

6)C,Here per the scientist 130 kg raw ore is processed to produce 1 gm pure gold

So avg ratio is 1/130*10^3 but in the question the ratio is 20 times so the new ratio is

20/130*10^3

So now with ideal rate i.e.:

130 kg raw ore ->1 gm gold
180*10^3*10^3 kg raw ore in 1 day ->

180/130 *10^3*10^3 gm gold in 1 day=
=1.38*10^3 kg gold in 1 day,which means
1.38 metric tons in 1 day,but in the question the depot which contains gold contains ore with 20 time the avg proportion of gold to ore,so 
Total gold produced in 1 day= 1.38*20= 27.6 metric tons gold in 1 day 
So 100 metric tons will be produced between 3 and 4 days

Posted from my mobile device

bM22 · Answer

I.
1. Chemicals were used to extract gold from the ore collected at the Grasberg mine. -  Implied  as mentioned in the para by the Environmentalist: "Because—unlike mining lode deposits—mining placer deposits does not usually involve crushing rock and using chemicals to extract gold, the environmental impacts are generally less than those of mining lode-deposits.". Also Grasberg is the largest mine in the world, implying it would have sufficient amount of lode deposits.

2.The Grasberg mine processed approximately 130 kilograms of raw ore for each 1gram of pure gold it produced. -  Not Implied , as it could be, we have not be given the data of how much raw ore is extracted from the mine, and if all gold only comes from Lode Deposits.

3. The Grasberg mine was located at or adjacent to a river.  Not Implied , cannot be deduced either from the passage or from the question.

II.
1.Each lode deposit is located on a river upstream from a placer deposit. -  Not Justified  as, what's mentioned is: "Such deposits are located where they were originally deposited by the mineral-bearing solutions that carried the gold up from the earth’s interior. Placer deposits, on the other hand, come from preexisting lode deposits that are exposed at the surface of the earth.", implying opposite of what's mentioned is justified.
 
2. Some lode deposits were created by placer deposits building up in a location over time - Again,  Not justified , reason same as mentioned above.

3. Placer deposits are likely to be located within the paths of present or former rivers. -  Justified. , as can be inferred from the Prospectors statement: " Placer deposits, on the other hand, come from preexisting lode deposits that are exposed at the surface of the earth. These lode deposits’ exposure to the weather causes gold to be released from the surrounding rock and transported by rivers in the form of dust or flakes."

III. 
3. For which one of the following questions concerning the time the passages were written does the information provided supply the clearest answer?
Correct Answer - D, as its explicitly mentioned in the passage in the environmentalist's statement.
The rest of questions cannot be answered as we would need more info.

IV.
1. Placer deposits are, on average, larger than lode deposits. -  No , as the opposite of what's mentioned is true.

2. Mining placer deposits sometimes has environmental impacts beyond habitat destruction and sediment release. -  Yes , as mentioned that "the environmental impacts are generally less than those of mining lode-deposits. The primary impacts of placer-deposit mining are habitat destruction and sediment release.", so the effects could be more.

3. Gold production from placer deposits makes up only a few percent of total production primarily due to increased quantities of gold being produced from lode deposits. -  No . Again, opposite of what's mentioned is the case.

V.
1. On average, an operation mining a lode deposit processes approximately 130 kilograms of raw ore to produce 1 gram of pure gold. -  Not supported , as no evidence is provided to support the same.

2. Modern commercial placer-deposit mining operations tend to use settling ponds to prevent the discharge of large amounts of silt and sediment. -  Not supported , again only claim is mentioned is mentioned, no evidence is mentioned to the support the claim.

3. Modern commercial lode-deposit mines are massive operations. -  Supported  - as mentioned in the statement by the environmentalist : "Unlike placer-deposit mines, modern commercial lode-deposit mines are massive operations, some displacing and processing up to 180,000 metric tons (1 metric ton = 1,000 kilograms) of raw ore per day."

VI.
Now the raw ore mined per day : 180,000 metric tons (1 metric ton = 1,000 kilograms) of raw ore per day.
Now, 130 kilograms of raw ore to produce 1 gram of pure gold. => the given proportion of gold to ore = 1/130000 gm.
=>: 20(1/130000).

In 1 day, the ore mined = 1800000 metric tons. = 180000000 kg of ore => ((1/130000)*180000000000)gm of Gold => 1.38*10^3 kgs => 1.38 Metric ton of Gold would be mined in 1 day.
Now 20(1.38) metric ton = 27.59 metric tons of gold is produced in 1 day. 
So, 100 metric tons would be produced in: (1/27.59)* 100 = ~ 3.62 days

Answer :  C  :  Greater than 3 but less than 4 days.

Sajjad1994 · Answer

Official Explanation

1. The Grasberg gold mine in Papua Indonesia is the largest gold mine in the world, producing over 57,000 kilograms of pure gold per year. For each of the following, select Implied if the information provided implies that, at the time the passages were written, it was likely true of the Grasberg mine. Otherwise select Not implied.

According to the environmental scientist, unlike placer-deposit mines, modern commercial lode-deposit mines are massive operations. Given that the Grasberg mine is the largest in the world, it is more likely to be a lode-deposit mine than a placer-deposit mine. Again according to the environmental scientist, unlike mining lode deposits—mining placer deposits does not usually involve crushing rock and using chemicals to extract gold, which implies that these are typical practices for mining lode deposits.

The correct answer is Implied.

As discussed in the analysis above, the environmental scientist’s statements suggest that the Grasberg mine is most likely a lode-deposit mine. Although the environmental scientist states that on average, such mining operations process approximately 130 kilograms of raw ore to produce 1 gram of pure gold, there is no information given to suggest that production at the Grasberg mine approximates that average.

The correct answer is Not implied.

As discussed in the analysis above, the environmental scientist’s passage implies that the Grasberg mine is most likely a lode-deposit mine. But the prospector’s passage implies only about placer deposits that they are always associated with rivers. There is no mention of a necessary relationship between lode deposits and rivers. Therefore, the information provided does not imply that the Grasberg mine was located at or adjacent to a river.

The correct answer is Not implied.

2. For each of the following, select Justified if it is a justified inference on the basis of the information provided. Otherwise select Not justified.

The prospector’s statements indicate that placer deposits are created when exposed lode deposits are weathered and the gold released is transported down rivers—thus indicating that all placer deposits form downstream of lode deposits. But there is no mention of a necessary relationship between lode deposits and rivers.

The correct answer is Not justified.

As noted in the analysis above, placer deposits are created by the weathering of lode deposits. According to the prospector’s passage, lode deposits are created by mineral-bearing solutions that carried the gold up from the earth’s interior. There is no other mechanism given for the formation of lode deposits.

The correct answer is Not justified.

According to the prospector’s statements, placer deposits form where gold from weathered lode deposits is washed down rivers and deposited in sand as the stream slows. Hence, placer deposits are likely to be located in current or former riverbeds.

The correct answer is Justified.

3. For which one of the following questions concerning the time the passages were written does the information provided supply the clearest answer?

The average ratio of ore to pure gold is given, but there is insufficient information to determine the average amount of ore processed per mine per day (ruling out A). The percentage of total gold production in the US that comes from placer deposits is given, but there is insufficient information to determine what that quantity is, let alone what percentage of the world total comes from placer deposits (ruling out E and B). Chemicals used to extract gold are claimed to cause environmental damage, but the specific forms of that damage are not given (ruling out C). However, the environmental scientist’s passage clearly lists habitat destruction and sediment release as the principal forms of environmental damage attributable to mining placer deposits (D).

The correct answer is D.

4. For each of the following statements, select Yes if, according to the information provided, it was accurate at the time the passages were written. Otherwise select No.

The prospector’s statements describe lode deposits as large and indicate that they account for the majority of the gold mined. The environmental scientist draws a contrast between placer and lode mines, indicating that lode mines have a much larger environmental impact by virtue of their size, and referring to them as massive operations. Therefore, there is substantial information to suggest that placer deposits are, on average, smaller than lode deposits.

The correct answer is No.

That the environmental scientist describes habitat destruction and sediment release as the primary impacts of placer-deposit mining suggests that these do not constitute an exhaustive list of impacts. Therefore, it is reasonable to infer that mining placer deposits sometimes has impacts other than habitat destruction and sediment release.

The correct answer is Yes.

According to the prospector’s statements, placer deposits account for only a small percentage of total gold mined in the US because of a decrease in the number of such deposits that are readily available. There is no information given to suggest that an increase in production from lode deposits is the cause of this decrease either in the US or globally.

The correct answer is No.

5. Each of the following claims appears in the environmental scientist’s passage. For each, select Supported if the scientist cites specific evidence to support the claim. Otherwise select Not supported.

The environmental scientist makes this claim in the third sentence of the second paragraph but does not provide evidence anywhere to support this claim.

The correct answer is Not supported.

The environmental scientist makes this claim in the final sentence of the first paragraph but does not provide evidence anywhere to support this claim.

The correct answer is Not supported.

The environmental scientist makes this claim in the final sentence of the second paragraph and then indicates that modern commercial lode-deposit mines process up to 180,000 metric tons (1 metric ton = 1,000 kilograms) of raw ore per day, helping to illustrate the magnitude of such operations. Therefore, the passage offers specific evidence to support the claim that modern commercial lode-deposit mines are massive operations.

The correct answer is Supported.

6. Suppose that a mine is established on a lode deposit that contains ore with 20 times the average proportion of gold to ore. Which one of the following describes the number of days it would take for such an operation, working at the fastest rate described in the passages, to produce 100 metric tons of pure gold?

The environmental scientist indicates that, on average, lode-deposit mines process 130 kilograms of raw ore to produce 1 gram of pure gold. If this lode deposit has 20 times the average concentration of gold, it will take 130/20, or 6.5, kilograms of raw ore to produce 1 gram of pure gold. The fastest rate of processing listed in the passage is 180,000 metric tons (or 180,000,000 kilograms) of ore per day. At that rate, this mine would be able to produce 180,000,000/6.5 grams, which is approximately 27,680,000 grams (27.68 metric tons), of pure gold per day. Therefore, it would take 100/27.68 days, which is approximately 3.61 days, for this mine to produce 100 metric tons of pure gold working at this rate, which is greater than 3 but less than 4 days.

The correct answer is C.

AlphaCentauri4ly · Answer

AndrewN  For Q2:

"Each lode deposit is located on a river upstream from a placer deposit."

The passage clearly says that placer deposits are formed from lode deposits weathered and carried by rivers downstream. Then, isn't it logical to infer that every lode deposit is located somewhere upstream from a placer deposit ? Official explanation makes no sense to me. Even though, no relationship is explicitly mentioned, it can be clearly inferred from the definition of placer deposit alone. Please help.

"If Y can result only from X, then isn't it logically correct to infer that X caused Y?"

AndrewN · Answer

Hello,  AlphaCentauri4ly . Remember, you can only go by what the passage tells you, even when facing an inference question. What, exactly, does the passage tell us about the location of lode deposits and placer deposits, relative to each other? Since the Environmental Scientist discusses, well, the environmental impact of mining, we need to look at the Prospector instead:

All I see of interest in the way of a directional agent is  lode deposits' exposure to the weather . That description could very well include wind, and since when does wind have to blow in a single direction? Perhaps the wind blows one way at some point and deposits gold dust or flakes  upstream  of the original lode, to be deposited wherever. Note that the passage does not specify  downstream of the lode —it merely states that the gold is  transported by rivers , presumably from the point at which that gold makes contact with the water. Thus, we  cannot  make the inference that EACH  lode deposit is located on a river upstream from a placer deposit . Such an inference is too extreme and cannot be backed up by the passage.

The other two are easy. Nowhere does the passage indicate that lode deposits can be formed by placer deposits: the arrow of causality is backwards. Finally, I included the last line of excerpt above to show that the third inference is justified. A stream can slow and deposit gold dust or flakes  in pockets of sand , thereby creating a placer deposit. In short:

Watch out for associative reasoning. When you start to make your own assumptions, you can quickly let these questions get away from you. Thank you for thinking to ask me about this question, one I had not seen before. Good luck with your studies.

- Andrew

Abhivas · Answer

chetan2u .
Sir,
 Please explain b option of question 1. 
 since we are discussing probability in this option. why it cannot be in this particular option.

chetan2u · Answer

Hi, I would say the question is a bit more than merely a probability question.
The answer could easily in that scenario be 120kg for 1 kg of gold or 200 kg for 1 kg of gold or 10 kg for 1 kg gold.

What we are looking for is whether something in the para justifies the option. Average does not speak on the probabiliy of something being exactly at the average.

Maybe, if it said that many big mining companies are able to get 1 kg gold from 130kg ore. We could have extended this to this big company too.

Sa800 · Answer

someone help me out…in these problems it looks like you either need one or the other passage to answer the questions…. I don’t think I’ve come across a problem where you need to read both passages to answer the questions….. is this true and has anyone else noticed this too??

chetan2u · Answer

The questions in MSR can easily refer to two or more tabs. 
The answer may require referring to more than one passage.

Posted from my mobile device

boybread5 · Answer

KarishmaB , I saw your Youtube video on MSR around note-taking. I can see the appeal of taking notes for tabs that involve numbers (such as the example in your Youtube video with drivers vs. diodes), but the first tab is loaded with a ton of qualitative information. Are you still note-taking the first tab if you're doing this problem? What info are you taking notes on then?

Trying to pivot to this process given prior time crunch issues with MSR so really appreciate your help in advance!

KarishmaB · Answer

Notes are useful in MSR when the tab gives you generic information along with some specific numbers. You want to note down the numbers so that you don't need to flip through the tabs again and again. But when data is in the form of text as given here, visualization helps to understand and remember it. We cannot make notes here. This is like an RC passage. Since data in MSR can vary greatly, our approach will also need to vary. Here are some more MSR discussions with different approaches: https://youtu.be/hdCH-U1p8dw https://youtu.be/xL631VXGjSg https://youtu.be/2cY39qHenc0 https://youtu.be/bql1Mw0gl_A https://youtu.be/pQmUy_r4SbM

Natansha · Answer

Hi  KarishmaB , could you please help how in the first ques, the first point ''Chemicals were used to extract gold from the ore collected at the Grasberg mine.'' is implied. Even if Grasberg mine is the largest, it could have easily been placer deposits mine or lode deposits mine, we can't surely say it to be lode deposits mine, and hence we can't say if chemicals were used to extract

KarishmaB · Answer

Here is what we are given: 
  Mining lode deposits has a much larger environmental impact by virtue of the size of such operations, ...
Unlike placer-deposit mines, modern commercial lode-deposit mines are massive operations ...

So the placer deposit mines are small ops while lode deposit mines are massive. So the largest gold mine would be lode-deposit one.

mkeshri185 · Answer

I did not get the explanation of Q1

For Q1 2nd part : In 1st part you assumed this 57000 kg producing mine to be Lode mine. But now you are saying we can't say about whether they followed the avg rate or not. How can it be possible. Also it is talking about approximation. If you say we cant say for sure then Q1 part 1 is also not sure. No where it is written that 57000 will be produced by the Lode mine. It is just said that higher proportion comes from Lode mining but we dont know how much is the higher. So at one place you are assuming something and in the very next line you are saying ' it is not mentioned explicitly'? Also in part 1 of Q1 it you are greeing that this particular mine is using chemicals but how can we assume so? What if they are not using chemicals? It was never said that this particular mine used chemicals---(as per your logic in part 2). so in same manner we can say that this mine producer did not follow the average. So it will be either Not justified for both or Justified for both

That's so frustrating. How can you decide you have to assume something or not
   Sajjad1994

Bunuel · Answer

From Tab 2, modern lode mines are massive operations with huge throughputs; from Tab 1, placer is river-pocket dust/flakes and now only a few percent of production. A mine that is the largest in the world fits the lode profile far better than the placer profile, so “Implied” means likely lode, not certain. If likely lode, Tab 2 says lode mining uses toxic chemicals, so chemicals are implied.

The 130 kg per gram number is explicitly an average in Tab 2; there is no Grasberg-specific grade, so that rate is not implied for this mine.

The 130 kg per gram number is explicitly an average in Tab 2; there is no Grasberg-specific grade, so that rate is not implied for this mine.

mkeshri185 · Answer

So from the keyword 'Largest Mine' you are saying it should be Lode Mine which i absolutely agree. So your thinking is Since it is larget so it is "LIKELY' to be Lode Mine which is perfectly fine.

But for the next Part 3 , It is again the Largest Mine -> Lode Mine. And it is explicitly said that 'this kind of process.....' approx takes 130kg of raw ore to produce 1g of pure gold. So why is this wrong? I am using the same logic as you...

your logic:- Largest Mine-> Likely to be Lode Mine -> so might be using chemical = perfect
My logic for 3rd part :- Largest Mine -> Likely to be Lode Mine - > so it might take approx 130kg of raw ore to prod 1g of pure gold

Why is this wrong then? the first 2 part of the arrow are same for me and you and the 3rd part is also true if it is lode mine. It is Like A(Lode Mine) has 2 factors 
B(Chemical has been used) and C (takes approx 130kg of raw ore to prod 1g of pure gold). so both B and C are linked with A. and you are assuming A->B but not A->C?

Bunuel · Answer

Largest mine makes it likely to be a lode mine because Tab 2 describes modern lode operations as massive. Once lode is likely, chemicals are likely, since Tab 2 says the lode process involves crushing rock and using toxic chemicals.

The 130 kilograms per gram figure is explicitly an average across lode operations in Tab 2. An average does not make a specific site likely to have that exact rate. Largest tells you about capacity and scale, not ore grade. Tab 2 also signals variation across mines by giving extreme daily throughputs, which means sites differ. So part 3 is not implied. For your step to work, the text would need to say every lode mine processes about 130 kilograms per gram, and it does not.

mkeshri185 · Answer

For your step to work, the text would need to say every lode mine processes about 130 kilograms per gram, and it does not.

so then for chemical part also it should say that every Lode mine uses chemical. which is not said in the passage

Bunuel · Answer

I'll try once more.

Chemical use is described as part of how lode mining works, not as something that varies. The passage says “mining lode deposits involves crushing rock and using toxic chemicals,” presenting it as the defining method.

The 130-kilogram figure, in contrast, is called an average, showing variation among mines. A defining process can be assumed for a likely lode mine; an average rate cannot. Hence chemical use is implied, but the 130-kilogram rate is not.

	How much raw ore did the average lode-deposit mine process daily?
	What was the total annual quantity of pure gold produced globally by placer-deposit mines?
	What were the principal forms of environmental damage attributable to chemicals used to extract gold from raw ore?
	What were the principal forms of environmental damage attributable to mining placer deposits?
	What was the total annual quantity of gold mined in the US?

	Greater than 1 but less than 2 days
	Greater than 2 but less than 3 days
	Greater than 3 but less than 4 days
	Greater than 4 but less than 5 days
	Greater than 5 but less than 6 days

Gold is typically mined from two different types of geologic formation

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Implied	Not Implied
		Chemicals were used to extract gold from the ore collected at the Grasberg mine.
		The Grasberg mine processed approximately 130 kilograms of raw ore for each 1gram of pure gold it produced.
		The Grasberg mine was located at or adjacent to a river.

Justified	Not Justified
		Each lode deposit is located on a river upstream from a placer deposit.
		Some lode deposits were created by placer deposits building up in a location over time.
		Placer deposits are likely to be located within the paths of present or former rivers.

Yes	No
		Placer deposits are, on average, larger than lode deposits.
		Mining placer deposits sometimes has environmental impacts beyond habitat destruction and sediment release.
		Gold production from placer deposits makes up only a few percent of total production primarily due to increased quantities of gold being produced from lode deposits.

Supported	Not supported
		On average, an operation mining a lode deposit processes approximately 130 kilograms of raw ore to produce 1 gram of pure gold.
		Modern commercial placer-deposit mining operations tend to use settling ponds to prevent the discharge of large amounts of silt and sediment.
		Modern commercial lode-deposit mines are massive operations.

Justified	Not Justified	Statements
	X	Each lode deposit is located on a river upstream from a placer deposit.
	X	Some lode deposits were created by placer deposits building up in a location over time.
√		Placer deposits are likely to be located within the paths of present or former rivers.

GMAT Multi-Source Reasoning (MSR) Questions

Gold is typically mined from two different types of geologic formation

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