Gems & Jewelry (GJ)
What the GJ candidate must know
Value in gems and jewelry rests on the four Cs - color, clarity, cut, and carat weight - plus certification (e.g., GIA, AGS reports) and provenance (designer or signed pieces). Know the difference between replacement value (retail, new, for insurance) and fair market value (used, secondary market, willing buyer/seller). This distinction is the single most tested idea in the domain.
Concepts to hold
Understand karat vs. fineness (24k = 100% gold; 18k = 75%), pennyweight and troy ounce conversions (20 dwt = 1 troy oz; 31.1035 g = 1 troy oz), and how metal content is valued against spot price with a scrap or refining discount. Know the major colored stones (ruby, sapphire, emerald) and that treatment disclosure (heat, fracture fill, diffusion) materially affects value. Understand that cultured pearls and synthetic/lab-grown diamonds have distinct value tiers and must be identified.
Traps in questions
- Using retail replacement value for an estate or divorce FMV assignment.
- Ignoring treatments or undisclosed synthetics.
- Mixing avoirdupois ounces with troy ounces when computing metal value.
- Assuming a brand name always adds value; condition and authenticity matter.
Worked rule of thumb
For a gold item: weight (g) ÷ 31.1035 = troy oz; × purity (e.g., 0.75 for 18k) × spot price = melt value. Then apply a scrap discount (often 10–30%) for used jewelry.