What is the value of an item, and how can its value be determined?
Most appraisers will weigh a piece of gold jewellery and multiply the weight by a factor that reflects their opinion of the current market value of gold jewellery. Many appraisers say that they then add something for "antique value" or appearance of the piece, but this is totally subjective. Although different appraisers would probably come up with close to the same gold weight, the value they assigned to the piece would be very different because:
All appraisers do not appraise gold at the same per-gram rate
Appraisers add their own subjective interpretation of the "antique value" of a piece
With gold jewellery, the price you can sell a piece of jewellery to a refiner or gold dealer is simple. Even though an appraiser may value a piece at $40 per gram, reflecting what you would have to pay for a comparable new piece in a retail store, gold always has a "scrap" price that relates only to the actual gold value in the piece. If your jewellery weighs 20 grams and the current scrap price for that carat gold is $6 a gram, you know your jewellery is worth at least $120 because you could sell it to a scrap gold buyer for that amount. It may be worth more than scrap because of its desirability to a potential buyer, but the floor price is the scrap value.
Be very careful when interpreting jewellery appraisals. An appraisal (at least one by a gemmologist) reflects what you would pay for a similar piece today in a retail jewellery store. It has nothing to do with what you can sell the item for unless you own a jewellery store. It is extremely rare that someone is willing to pay the full-appraised price for a piece of antique fine jewellery. If you can find a retail customer for this specific piece in question, you might be able to get somewhere around half the appraised value. If you sell to a dealer who will resell it, you would probably be offered the scrap value of the gold plus a bit extra, depending on the desirability and rarity of the item.
The following is a simple formula for determining the approximate scrap gold value:

18 carat formula: Spot Gold X 75% divided by 31.3 grams = $ value per gram
14 carat formula: Spot Gold X 58.3% divided by 31.3 grams = $ value per gram
10 carat formula: Spot Gold X 41.6% divided by 31.3 grams = $ value per gram.
  9 carat formula: Spot Gold X 37.5% divided by 31.3 grams = $ value per gram
You can get SPOT GOLD prices from TV financial new services, newspaper, internet etc but do not get Spot Gold confused with Gold Futures.
Gold is weighed in either Grams or Pennyweights.
There are 31.3 grams to a troy ounce, and 20 pennyweights in a troy ounce. Be sure you understand which is being used, and adjust the above formula accordingly.
These additional factors will affect the amount at which you can sell used gold jewellery:
  • If it is truly "scrap", i.e. not usable to anybody for anything, you can sell to a scrap gold dealer (often a jewellery store, coin dealer, or pawn shop… look in the yellow pages) for something below the dollar value given above, because (A) the dealer needs a little profit and when he sells it to the refiner, (B) the refiner needs a little profit. Dealers usually offer, for scrap, within the range of 50% to 80%. A note should be made here that many dealers deduct an additional percentage for chains or other jewellery which may contain a larger percentage of solder, for class rings which are often weighted with cement, and rings with unusually large, heavy glass or synthetic stones that add weight but not value.
  • If you are selling to a jewellery dealer, and the piece is usable, but not terribly saleable (because it is out of fashion or boring, or not well made, and doesn't have an antique or vintage value) you may get anywhere from slightly below actual dollar value above, to something above the dollar value. The dealer bases this on the judgement of saleability.
  • If you are selling to a jewellery dealer, or antique dealer, a piece that is a desirable or collectible antique or has good vintage value, the value will depend largely upon that dealer's view of its saleability in their particular market. As stated above, most often these pieces sell for considerably less than their retail appraised value no matter in what market they are sold to the retail buyer (for example, antique shop, antique show, pawn shop). This is one of the characteristics that make antique fine jewellery an excellent value for the consumer.
Some of this information applies in general to used fine jewellery set with various stones, enamel, etc; however, these guidelines are meant basically for simple gold pieces of relatively recent vintage. Obviously valuable stones will increase the amount a dealer is willing to pay for a piece of jewellery.