CGA Gemstone Treatments & Enhancements 1 — Questions and Answers
Question 1: Which treatment is most commonly applied to rubies and sapphires to improve their color and transparency?
- Fracture filling with lead glass
- Heat treatment (Correct answer)
- Beryllium lattice diffusion
- Surface coating
Correct answer: Heat treatment
Heat treatment is the most widely used enhancement for corundum gemstones, improving both color and clarity by dissolving rutile silk and altering trace element chemistry.
Question 2: Which organization publishes internationally recognized disclosure guidelines for gemstone treatments used by the trade?
- GIA (Gemological Institute of America)
- CIBJO (World Jewellery Confederation) (Correct answer)
- AGS (American Gem Society)
- ASA (American Society of Appraisers)
Correct answer: CIBJO (World Jewellery Confederation)
CIBJO publishes the internationally recognized Blue Books, which establish gem grading nomenclature and disclosure standards for treatments accepted by the global jewellery trade.
Question 3: Fracture filling in diamonds to improve apparent clarity is most commonly accomplished using which substance?
- Epoxy resin
- Cedar wood oil
- High-lead-content glass (Correct answer)
- Silicone polymer
Correct answer: High-lead-content glass
High-lead-content (lead) glass is injected into fractures to fill them; its refractive index close to diamond's makes the fractures nearly invisible, but the process is non-permanent.
Question 4: What does the acronym HPHT stand for in the context of diamond color treatment?
- High Polish Heat Technology
- High Pressure High Temperature (Correct answer)
- Hydrothermal Pressure Heating Technique
- Heat Processing and Hardness Testing
Correct answer: High Pressure High Temperature
HPHT (High Pressure High Temperature) treatment subjects diamonds to conditions that mimic the earth's mantle, permanently altering color by annealing structural defects responsible for undesirable tints.
Question 5: Beryllium diffusion treatment became a major trade concern in the early 2000s and is primarily associated with which gemstone?
- Emerald
- Ruby
- Sapphire (Correct answer)
- Alexandrite
Correct answer: Sapphire
Beryllium diffusion of sapphires was discovered around 2001–2002; the light element penetrates deep into the stone, producing dramatic orange, yellow, or padparadscha-like colors undetectable by standard gemological testing.
Question 6: Which gemstone is most widely treated with oil or resin fracture filling, making undisclosed treatment a common trade concern?
- Blue sapphire
- Diamond
- Emerald (Correct answer)
- Alexandrite
Correct answer: Emerald
Emerald is routinely fracture-filled with oils, resins, or polymers because the species almost universally contains surface-reaching fractures (jardin); the practice is so common it has its own grading scale.
Question 7: Which type of treatment involves exposing a gem to gamma rays, neutron bombardment, or electron beams to permanently change its color?
- Diffusion treatment
- Impregnation
- Irradiation (Correct answer)
- Bleaching
Correct answer: Irradiation
Irradiation alters the color center defects in a gem's crystal lattice by exposing it to nuclear radiation, producing new or intensified colors that may or may not be stable without subsequent heat treatment.
CGA Gemstone Treatments & Enhancements 1
Which treatment is most commonly applied to rubies and sapphires to improve their color and transparency?