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 Source - Prospector's Guide to Gold Deposits
| 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. Such deposits are located where they were originally deposited by the mineral-bearing solutions that carried the gold up from the earth's interior." |
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| "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." |
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| "Placer-deposit mines have historically been the source of approximately 35 percent of the total gold mined in the US." |
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| "However, in recent years, the quantity of gold mined from such deposits has decreased as the readily accessible deposits have been exhausted." |
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| "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." |
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Summary: This passage explains two types of gold deposits - lode (primary, pure deposits from earth's interior) and placer (secondary deposits from weathered lode deposits carried by rivers). US gold mining has shifted dramatically from placer deposits (35% historically) to predominantly lode deposits (placer now only "a few percent").
Understanding Source B: Text Source - Environmental Scientist's Report on Mining Impacts
| Information from Dataset | Analysis |
|---|---|
| "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." |
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| "The primary impacts of placer-deposit mining are habitat destruction and sediment release. Habitat destruction occurs as a result of river diversions and disruptions of river bottoms and banks" |
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| "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 of such operations, the generation of waste material, and the use of toxic chemicals." |
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| "On average, such mining operations process approximately 130 kilograms of raw ore to produce 1 gram of pure gold." |
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| "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." |
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Summary: This passage reveals the environmental trade-offs of the mining shift described in Source A. While placer mining causes localized river damage, lode mining creates much larger impacts through massive-scale operations (up to 180,000 metric tons/day), chemical use, and waste generation (130,000:1 ore-to-gold ratio).
Overall Summary
The combined sources reveal a complete story of US gold mining transformation:
- Gold mining has shifted from placer deposits (river-based, 35% historically) to lode deposits (now 95%+ of production)
- This shift occurred because easily accessible river deposits became exhausted
- The environmental cost increased dramatically - from localized river disruption to massive industrial operations processing 130,000 kg of ore for each gram of gold
- Modern gold mining prioritizes large-scale lode operations despite their "much larger" environmental impact, as they're now the primary remaining source for increased production
Question Analysis
The analysis evaluates three statements about the Grasberg mine based on information from two sources: a prospector discussing types of gold deposits and an environmental scientist comparing mining methods. The key challenge is determining what can be reasonably inferred about Grasberg's operations from the provided source material.
Connecting to Our Analysis
Our approach involves first establishing what type of mining operation Grasberg represents, then applying the source information about that mining type to evaluate each statement. The critical insight is that Grasberg's massive scale (world's largest gold mine producing over 57,000 kg annually) provides strong evidence about its operational characteristics.
Extracting Relevant Findings
Source A (Prospector) Key Points:
- Two types of gold deposits exist: lode and placer
- Lode deposits are large deposits of nearly pure gold from earth's interior
- Placer deposits are derived from weathered lode deposits, transported by rivers
- Placer mining has declined from 35% to just a few percent of US gold production
Source B (Environmental Scientist) Key Points:
- Placer mining typically doesn't use chemicals or crush rock
- Lode mining uses toxic chemicals and processes approximately 130 kg of raw ore per 1 gram of pure gold on average
- Modern lode mines are massive operations processing up to 180,000 metric tons daily
Grasberg Mine Classification Evidence:
The evidence strongly suggests Grasberg is a lode deposit mine because:
- Placer deposits now account for only a few percent of gold production
- The scale matches the "massive operations" described for modern lode mines
- Such high production volume (57,000 kg/year) would be unlikely from river-based placer deposits
Individual Statement Evaluations
Statement 1 Evaluation
"Chemicals were used to extract gold from the ore collected at the Grasberg mine."
- Evidence: Grasberg's massive scale (world's largest, 57,000 kg/year) indicates it's a lode mine
- Source correlation: Source B explicitly states lode mining uses toxic chemicals
- Supporting context: Placer mining (which doesn't use chemicals) accounts for minimal modern production
- Conclusion: This statement is IMPLIED by the available information
Statement 2 Evaluation
"The Grasberg mine processed approximately 130 kilograms of raw ore for each 1 gram of pure gold it produced."
- Evidence: Source B states this is an "average" for lode mining operations
- Key limitation: "Average" means some mines process more, others less than this ratio
- Logical gap: We cannot assume Grasberg exactly matches the industry average
- Conclusion: This statement is NOT IMPLIED by the available information
Statement 3 Evaluation
"The Grasberg mine was located at or adjacent to a river."
- Context: Rivers are associated with placer deposits, not lode deposits
- Source correlation: Lode deposits are found where originally deposited from earth's interior
- Classification evidence: Grasberg's characteristics indicate it's a lode mine, not a placer mine
- Conclusion: This statement is NOT IMPLIED by the available information
Systematic Checking
The analysis maintains logical consistency by first establishing Grasberg's classification as a lode mine based on its massive scale, then systematically applying the source information about lode mining characteristics. Each evaluation is grounded in specific evidence from the sources and follows clear reasoning chains. The distinction between what is directly stated versus what can be reasonably inferred is carefully maintained throughout.
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.