Formation – Main Lesson

Unit 2: How Gems Form

What’s This All About? 

Time to dig deep! Jake shows us how gemstones are born underground through nature’s amazing cooking process that takes millions of years.

Key Takeaways: 

• Gemstones form deep in Earth’s crust (the outer layer) and sometimes in the mantle (the layer below) 
• The three magic ingredients for gem formation are: heat, pressure, and sometimes water 
• Think of Earth as a giant oven – when rocks melt into magma and slowly cool down, gems can crystallize 
• Volcanic activity creates the perfect conditions for many gemstones to form over long periods 
• Pressure from moving tectonic plates helps squeeze rocks together, creating ideal gem-forming conditions 
• Water can seep into tiny cracks and fissures in rocks, carrying dissolved minerals with it 
• When the mineral-rich water evaporates or cools, it leaves behind crystals that can become gemstones 
• The cooling process must happen slowly for large, well-formed crystals to develop 
• The specific combination of temperature, pressure, and chemical conditions determines what type of gem forms 
• Different gemstones require different formation environments, which is why they’re found in specific locations worldwide

International Gem Society

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