The sale of your gold and diamonds separately
If you decide to remove the diamonds in your jewelry from gold and sell them separately, the price you will get for them will reflect their value as materials.

It is, you will not get any price premium based on the value of the project, the brand or the age of the jewelry.

Gold sale
You can sell the gold pieces of your piece to gold traders, who will buy the metal with the intention of merging it or reselling it at a refinery.

In such a case, the value of your gold can be loosely estimated by multiplying the weight of pure gold in the article by the market price of the metal per unit of weight.

As an example, if your gold piece is 14 carats, then it contains 58.3% pure gold (14K divided into 24K); if the piece weighs 10 ounces of troy (1 ounce of troy = 31.1 grams), then it contains 5.83 ounces of troy pure gold (10 x 58.3%).

5.83 multiplication from the current gold price per troy ounce will tell you how much your gold is worth.

However, keep in mind that the price the buyer will offer to your will usually be lower than your estimate as the dealer also needs to make a profit when your gold is resold.

This is why it is good to sell your gold to a trader who is closest to the end buyer so that he can get a better price.

Sale of diamonds
Once your diamonds are taken out of your gold jewelry, you can get them from a jeweler or diamond dealer to sell them. The price they will offer will depend on the characteristics of the diamonds as cut, blush, clarity and weight.

See: Selection of diamonds cleaned by the eye carefully examined for quality
However, you don’t have to wait to get the same price as the one you see in the store. Very often, you will actually get less than 50% of the price per minute because diamond buyers can purchase the same stones from their most suppliers at lower wholesale prices.

Not all jewelers buy diamonds, though. Your best choice is to ask around and compare the prices they offer.

You can also check out several diamond dealers and see how their offerings are comparable to those arrived from jewelry stores.

If it has no documents describing the quality characteristics of your diamonds, it is a good idea to value or graduate from a gem laboratory like that of the GIA (Gemological Institute of America).

This would provide some verification of the quality of your stones and help you in negotiating a better price.

The sale of your gold and diamonds together
Your second option is to sell your diamonds and gold together, as a complete piece of jewelry. This is recommended if your jewelry has a high value based on its antiquity, exceptional design, brand, etc.

In such a case, you may be able to get a higher price for the item if you sell the stones and metal separately.

The sale of your jewelry to merchants
Traders and refiners usually buy jewelry to knock it down, melt it or resell the metals and sell the stones.

Those buyers will not give you a price that is higher than what the materials of your jewelry are worth. It is, you will not get any extra money for the project or the age of your jewelry.

The sale of gold and diamonds to jewelry stores
Not all jewelers buy old jewelry for cash. Some jewelry stores can buy your items as complete pieces, but if they will give you a substantially better price than the cost of gold and diamonds as the materials are not certain and depend on the item.

Many jewelers will only buy your pieces with the intention of cutting them down and using the metal and stones, and these buyers will not give you a much higher price than what the merchants would offer you.

Auctions
You can always try to sell your jewelry at auction and see if they will get a better price than what the stores or dealers offer you. Online auction sites come in handy in such cases.

Just make sure your jewelry is clean and polished, and keep in mind that if you value it from a professional, the estimate document will help you justify the price you are asking for.