Podcast
Questions and Answers
What are the factor that affects the mining economics of gemstones?
What are the factor that affects the mining economics of gemstones?
- Geological conditions during mountain building
- Demand and political climate
- Type of deposit
- Labor costs and environmental concerns, and Demand and political climate (correct)
Where do most colored stones form?
Where do most colored stones form?
- In the earth's oceanic crust
- In volcanic rocks
- In the earth's continental crust (correct)
- In pegmatites
What does the size of crystals in igneous rocks indicate?
What does the size of crystals in igneous rocks indicate?
- The pressure of the water
- The presence of gems
- The speed of cooling (correct)
- The type of deposit
What is the advantage of secondary deposits compared to primary ones?
What is the advantage of secondary deposits compared to primary ones?
What is the role of superheated, pressurized water in gem formation?
What is the role of superheated, pressurized water in gem formation?
What is the outcome of thousands of tons of eroded rock being mined?
What is the outcome of thousands of tons of eroded rock being mined?
Where are some of the largest and most perfect gem crystals found?
Where are some of the largest and most perfect gem crystals found?
What is true of igneous rocks?
What is true of igneous rocks?
What type of gems end up in the secondary deposit?
What type of gems end up in the secondary deposit?
Study Notes
Gemstone Formation
- Rocks are the raw materials for gemstone formation
- Most colored stones form in the earth's continental crust
- Geological conditions during mountain building are favorable for gem formation
- Understanding gemstone formation helps prospectors pick the right places to look for gems
Rock Types and Gem Formation
- In igneous rocks, large crystals indicate slow cooling, while small crystals indicate rapid cooling
- Some types of volcanic rock can transport existing gems from deep in the crust to the earth's surface
Pegmatites and Gem Formation
- Some of the largest and most perfect gem crystals come from pegmatites
- Pegmatites are a type of igneous rock that forms during the final stages of a magma chamber's cooling process
Secondary Deposits and Gem Mining
- Secondary deposits are easier to work than primary ones and might contain greater concentrations of gems
- Only the toughest gems survive to become part of secondary deposits
- Thousands of tons of eroded rock might yield only a few ounces of gem material
Mining Economics
- Mining economics are affected by demand, political climate, labor costs, environment, accessibility, type of deposit, and mining methods
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