A Lao Fengxiang ring described as “ZG18K, 2.56 g, diamond 0.16 ct, VVS/K–L” needs two checks before pricing: what the weight field includes, and what the grading document actually says. Do not turn these few numbers into a current quote.
18K describes the gold alloy; ZG needs its own confirmation
18K nominally means 18 parts gold out of 24, or 75% gold in the alloy. White gold is a gold alloy, not platinum. The FTC precious-metal jewelry guide explains this karat system. The letters “ZG” in a transcription do not by themselves establish a universal purity or brand-authentication rule; compare the actual engraving with the invoice.
Does 2.56 g include the diamond?
A 0.16 ct diamond weighs 0.032 g. If 2.56 g is the complete ring's gross weight, there is only that stone, and the rest is verified 18K alloy, the estimated metal weight is 2.56 − 0.032 = 2.528 g. Its nominal fine-gold content would be 2.528 × 0.75 = 1.896 g.
If 2.56 g already means net gold-alloy weight, do not subtract the diamond: the corresponding fine-gold figure would be 1.92 g. Neither calculation replaces weighing and material checks. Additional components or a mistranscribed weight can change both.
What VVS and K–L can tell you
Read the report's issuer, scope and whether it grades a mounted piece or a loose diamond. VVS and a K–L range on a jewellery document should not automatically be turned into an exact VVS1/K loose-stone grade. K–L is warmer than the highest colour grades on the GIA D-to-Z scale, but appearance also depends on setting, lighting and cut.
The GIA diamond grading report guide explains how quality is documented. Its GIA natural diamond reports and services page also distinguishes report products. A grading document describes an item; it is not a promise of a buyer's price.
Compare offers on the same basis
For metal recovery, request accepted weight, fineness, per-gram rate and itemised deductions. Check whether the rate is for 18K alloy or fine gold before applying a purity factor. For a complete-ring sale, ask separately about the diamond, setting condition and any value attributed to purchase documentation.
For a store exchange, obtain the actual branch's written terms: an exchange credit tied to buying a new ring is different from cash paid for the old one. Compare quotes dated the same day and avoid using the original retail price as a guaranteed resale floor.