MeltValue.com

Gold Filled Calculator

The gold calculator on this page is only applicable for solid gold jewelry, however it may be used for gold filled jewelry with some modifications to your calculation.

Firstly, look at the piece of jewelry you suspect is gold filled to see if there are any hallmarks to indicate the fraction used - usually 1/20 or 1/10.

Next, note whether it is gold filled "single" or "double" sided - this indicates whether the gold filled is on one side or two sides.

The possible combinations that you can have are:

• Single sided, 1/20 - This means 1/40 (2.5%) of the item's total weight is the hallmarked gold purity.
• Single sided, 1/10 - This means 1/20 (5%) of the item's total weight is the hallmarked gold purity.
• Double sided, 1/20 - This means 1/20 (5%) of the item's total weight is the hallmarked gold purity.
• Double sided, 1/10 - This means 1/10 (10%) of the item's total weight is the hallmarked gold purity.

For example, a 10 gram 18K solid gold piece of jewelry would be 75% pure gold (or 7.5g of gold). The amount of gold for the equivalent 18K gold filled jewelry would be:

• Single sided, 1/20 18K - (10g x 750/1000 x 1/2 x 1/20 = 0.1875 g of pure gold) - 2.5% of solid gold equivalent
• Single sided, 1/10 18K- (10g x 750/1000 x 1/2 x 1/10 = 0.375 g of pure gold) - 5% of solid gold equivalent
• Double sided, 1/20 18K - (10g x 750/1000 x 1/20 = 0.375 g of pure gold) - 5% of solid gold equivalent
• Double sided, 1/10 18K - (10g x 750/1000 x 1/10 = 0.75 g of pure gold) - 10% of solid gold equivalent

Hence, to use the gold calculator for determining the value of gold filled jewelry, you simply need to multiple the respective factor above of 2.5% (2.5/100), 5% (5/100), 5% (5/100), or 10% (10/100). To do this, you can either multiple this factor on the weight and enter the result into the weight (for instance, from above, for the first example, instead of 10 g put 0.25 g or 2.5% of 10g) or you may choose to put the percentage into the percentage of market value (use 10 g but instead of 100% of market value use only 2.5%).

Lastly, please be aware that gold hallmarks are sometimes faked and therefore may not be a reliable indicator of gold content.

Gold Color Types

Pure gold is generally considered too soft to be made into jewelry. To make gold more practical for jewelry, it is mixed with other metals to form a gold alloy. The following are the most common gold color types:

• Yellow gold - a mixture of gold, silver, copper, and zinc.
• White gold - a mixture of gold and one or more white metals such as platinum, palladium, nickel or zinc.
• Rose gold - a mixture of gold, copper, and silver.
• Green gold (or Electrum) - a mixture of gold, silver, and sometimes copper.

Gold Plating

Please be aware that the gold calculator is for solid gold jewelry. Solid gold jewelry contains a uniform mixture of gold and other metals throughout the entire piece of jewelry. For instance, a 10g piece of 18 karat (750) solid gold jewelry contains 75% gold or 7.5 g of pure gold.

On the other hand, gold plated jewelry contains almost no gold - except gold filled jewelry. Gold is an expensive metal and it is cheaper to use other metals to make jewelry. To make gold jewelry more affordable whilst enjoying the aesthetic appeal from the color of gold metal, a very small amount of gold can be applied to the exterior of the jewelry instead of using it uniformly through the jewelry. Hence, gold plated jewelry is usually a fraction of the cost of solid gold jewelry.

• Gold layered - a very thin layer of gold.
• Gold leaf - a very thin sheet of gold metal is wrapped or glided over the jewelry.
• Gold plated or gold electroplated - uses an electric current and a piece of jewelry, which acts as an electrode, inside a gold solution. The gold forms a coherent metal coating on the electrode.
• Gold filled or gold overlay or rolled gold plated - Uses a heat or pressure bonding process to mix and bond the metals together. The term gold filled is supposed only be used if it contains more than 5% of the item's total weight, whereas using the terms gold overlay or rolled gold plated may be used if the gold makes up less than 5% of the item's total weight - please read Wikipedia's gold-filled jewelry article for more information.
• Vermeil (pronounced ver-may) - gold plated sterling silver (92.5% silver).

To recap, gold plated jewelry contains an almost negligible amount of gold metal (with the exception of gold filled jewelry - see next section below for more information). The gold calculator is only applicable to solid gold jewelry, not gold plated jewelry.

Gold Hallmarks

A hallmark is a mark stamped on a piece of jewelry certifying the purity of metal used. There are hallmarking laws that apply to the sale of gold jewelry in some countries (such as the Hallmarking Act 1973 in the UK). However, globally there is no standard that must be followed therefore solid gold jewelry may or may not be hallmarked.

Solid Gold Hallmarks

Solid gold jewelry will have its purity stamped on it. The purity is expressed in karats (K or KT) which is expressed as fractions of 24 karat (pure gold) or the fineness scale which is expressed as parts gold per thousand. Please refer to the scrap metal price table for the relationship between karat and fineness.

Please be aware that gold jewelry may be hallmarked a certain karat and may not have that level of gold content (a lower karat rating) or may not be solid gold jewelry at all. Hence gold jewelry needs to be tested when valuing its gold metal content.

Gold Plated Gold Hallmarks

When inspecting gold jewelry, look for any noticeable discoloration, particularly around edges where more friction occurs. If you do notice discoloration or changes it its reflectivity, it is probably gold plated. Also take note of how heavy the jewelry feels, as gold is more dense than most common metals.

• Gold plated or gold electroplated - "GP", "G.P", "GEP", "HGP" or "G.E.P".
• Gold filled - "GF" or "G.F".
• Vermeil - "925", ".925", or "S925"

You may choose to scratch a suspected plated piece deep enough to see the underlying metal to confirm the jewelry is not solid gold. As this is a destructive test, choose a discreet spot which will not be visible when worn, for example, around the clasp on a gold chain.

Gold Testing

As a gold buyer this is important to remember gold metal is expensive relative to most other metals therefore there is always an economic incentive to pass lower content gold as higher content gold. Hence, remember to test for gold purity.

Touchstone Testing

This test involves the use of strong acids so before you begin this test, please ensure you have the personal protective equipment (PPE).

• Safety goggles - to protect your eyes
• Protective gloves - to protect your hands
• Water, baking soda, paper towels - to dilute, neutralize, and clean acid spills respectively.

Also ensure you are in a well-ventilated area as the acids are strong and noxious.

This test involves rubbing the jewelry on a touchstone, an abrasive stone similar to fine sand paper, leaving behind some metal from the jewelry. The gold testing kit will have different strengths of nitric acid, the higher the karat rating the stronger the acid. Start with the lowest strength acid (lowest karat rating) and work upwards. If the acid does not dissolve the metal left of the touchstone after after 20 to 40 seconds, then it means that it is a higher karat then the test. Continue testing until it does dissolve, then you can confirm that the karat rating is between the previous rating tested and the test that dissolved the metal. Not a definitive test for the exact karat rating, but simple and cost effective.

A couple of things that may help you do this test is to use a gold test needle (see section on miscellaneous equipment below) to use as a reference. Draw lines with the reference needle along with a line with the jewelry being tested, and test the acids perpendicular to the lines. This will make the test result more obvious seeing the result side by side a known gold content.

If you notice a highly effervescent green reaction then this indicates base metals and not solid gold jewelry.

X-Ray Fluorescence

This method of testing is non-destructive and is suitable for normal assaying requirements. A computer, called a x-ray fluorescent (XRF) analyzer, will use x-rays to determine the composition the the jewelry. It takes less than a few minutes to complete and the results may be printed out. Popular brands include Thermo Scientific Niton range or Olympus GoldXpert or DELTA Precious Metals XRF analyzers.

There is also a method called x-ray fluorescence assay which involves melting a sample into a uniform composition before testing the sample on a XRF analyzer. This method is more accurate then a XRF analyzer but less accurate then a fire assay.

Fire Assay

This method of testing is totally destructive however provides the greatest accuracy. The first part of the process is called fusion which involves mixing the sample with a fluxing agent (which helps melt, fuse, and separate the precious metal) and heating it to a high temperature. The second part of the process is called cupellation which involves using a collector, such a nickel or lead, to extract the precious metals.

The precious metals extracted from fire assay is then analyzed by one of the following methods:

• Flame Atomic Absorption (AA)
• Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES)
• Inductively Coupled Plasma-Mass Spectrometry (ICP-AES)
• Instrumental Neutron Activation Analysis (INAA)

Miscellaneous Equipment

Other equipment that is common in gold testing kits include:

• Jewelers loupe provides magnification to see small details more closely. Handy for inspecting hallmarks.
• Digital scale for precisely measuring the weight of jewelry.
• Magnet for testing if there are magnetic metals in the jewelry.
• Gold test needles for using as a reference in conjunction with the jewelry on the touchstone test.
• Diamond tester for confirming a precious stone is a genuine diamond (or moissanite).