Gem Identification with Simple Tools – Main Lesson

Unit 8: Gem Identification with Simple Tools

What’s This All About? 

More detective tools! Jake shows us specific tests using household items to help identify real gemstones from imitations.

Key Takeaways: 

• Read-through test (diamond vs. imitation separation only):
  • Only works on well-cut, round brilliant cut, colorless stones outside of settings
  • Place stone table-down over clear printed text
  • Real diamonds show zero read-through due to their optical properties
• Important limitation: Cut quality, shape, and proportions greatly affect results
  • Can help separate diamonds from CZ, synthetic moissanite, GGG, YAG, zircon
  • Synthetic moissanite and rutile can be distinguished by their higher fire/dispersion 
• Scratch test (use with extreme caution):
  • Warning: Most professionals refuse to use this on finished gemstones due to damage risk
  • Recommended only for rough, unfinished rock specimens
  • Hardness scale interpretation:
    • Fingernail scratches it = very soft (1-2 on Mohs scale)
    • Steel nail scratches it but can’t scratch glass = medium (3-5 on Mohs scale)
    • Can scratch glass but steel nail can’t scratch it = hard (6-9 on Mohs scale)
  • Remember: Many rocks contain multiple minerals, so test the right area
  • Repolishing damaged gems is expensive and reduces their value 
• Water immersion test:
  • Submerging gems in water changes how we

International Gem Society

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