Gemstone Identification & Classification Flashcards
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Read the first 7 Gemstone Identification & Classification flashcards as text
Which simple test helps separate natural amber from most plastic imitations?
Answer: It floats in saturated salt water
Amber's low SG (about 1.08) lets it float in saturated salt water, while most plastics sink.
Which of these is NOT an organic gem material?
Answer: Lapis lazuli
Lapis lazuli is a rock made mainly of lazurite, while the others are formed by living organisms.
A six-rayed star in sapphire results from rutile needles oriented in how many directions?
Answer: Three
Three sets of needles crossing at 60° each produce two rays, giving a six-rayed star.
Immersion showing color concentrated at facet junctions and the girdle suggests which treatment in sapphire?
Answer: Surface diffusion
Surface diffusion adds color only in a thin outer layer, which concentrates along facet edges.
A thermal conductivity diamond tester cannot reliably separate diamond from:
Answer: Synthetic moissanite
Moissanite conducts heat almost as well as diamond, so electrical-conductivity or dual testers are needed.
Peridot is the gem variety of which mineral?
Answer: Olivine (forsterite)
Peridot is gem-quality olivine, mainly forsterite, with high birefringence of about 0.036.
Which gem is known for a sharp diagnostic absorption line at 653.5 nm in the spectroscope?
Answer: Zircon
Zircon commonly shows a sharp line at 653.5 nm caused by uranium.
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