Gold is typically mined from two different types of geologic formations (known as deposits): lode deposits and placer deposits. Lode...
GMAT Multi Source Reasoning : (MSR) Questions
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.
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.
OWNING THE DATASET
Understanding Source A: Text - Technical Article by Prospector
| Information from Dataset | Analysis |
|---|---|
| "Gold is typically mined from two different types of geologic formations (known as deposits): lode deposits and placer deposits." |
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| "Lode deposits are what prospectors dream of finding: large deposits of nearly pure gold... located where they were originally deposited" |
|
| "Placer deposits... come from preexisting lode deposits that are exposed at the surface... gold... transported by rivers in the form of dust or flakes" |
|
| "Placer-deposit mines have historically been the source of approximately 35 percent of the total gold mined in the US" |
|
| "in recent years, the quantity of gold mined from such deposits has decreased... now accounts for only a few percent of total gold mined" |
|
Summary: The prospector explains that gold comes from two deposit types - lode (original, concentrated) and placer (eroded, in rivers) - with placer mining declining dramatically from 35% to just a few percent of US production due to depletion.
Understanding Source B: Text - Environmental Impact Report by Environmental Scientist
| Information from Dataset | Analysis |
|---|---|
| "mining placer deposits does not usually involve crushing rock and using chemicals... environmental impacts are generally less" |
|
| "primary impacts of placer-deposit mining are habitat destruction and sediment release" |
|
| "Modern commercial operations tend to use settling ponds to prevent this discharge" |
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| "Mining lode deposits has a much larger environmental impact by virtue of the size... generation of waste material... use of toxic chemicals" |
|
| "approximately 130 kilograms of raw ore to produce 1 gram of pure gold" |
|
| "modern commercial lode-deposit mines... some displacing and processing up to 180,000 metric tons... of raw ore per day" |
|
Summary: The environmental scientist reveals that while placer mining is much less environmentally damaging (no chemicals, just sediment), the industry has shifted almost entirely to large-scale lode mining which processes massive amounts of rock with toxic chemicals - explaining why the less harmful method has nearly disappeared.
Overall Summary
- The gold mining industry faces a fundamental conflict between resource availability and environmental impact
- Easily accessible placer deposits that made up 35% of US gold production have been exhausted
- The industry has been forced to shift almost entirely to lode mining despite it being far more environmentally damaging
- Modern lode operations must process \(\mathrm{130,000}\) times more rock than the gold they extract
- Operations scale up to 180,000 metric tons per day using toxic chemicals
- This shift demonstrates that economic necessity and resource depletion override environmental considerations in determining mining methods
Question Analysis
The question requires evaluating three statements about the Grasberg mine based on information about gold mining types and methods. The analysis must determine what can be reliably implied from the given sources about lode deposits, placer deposits, and their respective characteristics.
Connecting to Our Analysis
Our approach involves first understanding the two types of gold deposits described in the sources, then determining which type the Grasberg mine represents based on its scale and production capacity, and finally evaluating each statement against this classification and the specific information provided about mining methods.
Extracting Relevant Findings
Source A (Prospector) Key Points:
- Two types of gold deposits: lode deposits (large deposits of nearly pure gold from earth's interior) and placer deposits (gold released from exposed lode deposits and transported by rivers)
- Placer deposits historically accounted for 35% of US gold mining but now only represent a few percent due to exhaustion of accessible deposits
- This shift indicates most modern large-scale gold mining involves lode deposits
Source B (Environmental Scientist) Key Points:
- Placer mining does not usually involve crushing rock or using chemicals; primary impacts are habitat destruction and sediment release
- Lode mining uses toxic chemicals to extract gold and processes raw ore (gold aggregated with other minerals)
- Key statistic: On average, lode mining operations process approximately 130 kg of raw ore per 1 gram of pure gold
- Modern commercial lode mines are massive operations, some processing up to 180,000 metric tons of raw ore daily
Information Integration:
The Grasberg mine produces over 57,000 kg of pure gold annually, making it the world's largest gold mine. This massive scale strongly suggests it's a lode deposit mine because placer deposits now account for only a small percentage of gold production, readily accessible placer deposits have been exhausted, and only lode mines operate at the massive scale described in the sources.
Individual Statement/Option Evaluations
Statement 1 Evaluation
Statement: "Chemicals were used to extract gold from the ore collected at the Grasberg mine."
- Criteria: Determining whether chemical use can be inferred from the mine's classification and source information
- Evidence analysis: Given Grasberg's status as the world's largest gold mine, it must be a lode deposit operation
- Source connection: Source B explicitly states that lode mining uses toxic chemicals to extract gold
- Logical reasoning: Since Grasberg is almost certainly a lode mine based on its massive scale, and lode mining uses chemicals according to the source, chemical use is implied
- Conclusion: This statement is IMPLIED
Statement 2 Evaluation
Statement: "The Grasberg mine processed approximately 130 kilograms of raw ore for each 1 gram of pure gold it produced."
- Criteria: Whether the average ratio applies specifically to the Grasberg mine
- Evidence analysis: Source B states this is an average ratio for lode mining operations
- Specificity consideration: Individual mines can have different ore grades and processing ratios
- Logical reasoning: The passage doesn't imply this specific ratio applies to all lode mines, only that it's an average across the industry
- Conclusion: This statement is NOT IMPLIED
Statement 3 Evaluation
Statement: "The Grasberg mine was located at or adjacent to a river."
- Criteria: Location requirements based on deposit type
- Evidence analysis: Lode deposits are found where originally deposited by mineral solutions from earth's interior
- Deposit type distinction: Only placer deposits are necessarily associated with rivers due to transport processes
- Logical reasoning: Since Grasberg is almost certainly a lode mine, there's no basis to infer river proximity from the given information
- Conclusion: This statement is NOT IMPLIED
Systematic Checking
The analysis confirms that only the first statement about chemical use can be reliably inferred from the given information. The classification of Grasberg as a lode mine (based on its massive scale) directly connects to the source information about lode mining using toxic chemicals. The other two statements lack sufficient support from the passages - the 130kg ratio is presented as an average rather than a universal standard, and river proximity is only required for placer deposits, not lode deposits.
Final Answer
- Statement 1: Implied
- Statement 2: Not Implied
- Statement 3: 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.