We are often asked how do I find out the purity of my gold or How do I test the quality of my gold. Here we discuss three different and popular methods used widely to test the purity of gold - including Stone (hand test), Fire Assay and X-RF or X-ray Fluorescence. This is to give a brief idea to our customers on how jewelers determine purity of gold jewelry. Each test method is detailed along with their pros and con. Read to further understand which method we prefer at Totaram Jewelers and why...
1. Stone (Hand Test) :
This is the simplest gold purity test and probably not very accurate, but is performed at most pawn shops and has been in use since ancient times. The central tool in the stone hand test is a touchstone (hence the name) which is usually a dark hard stone with a finely grained surface. When soft metals like gold are drawn across it, they leave a visible line. The color of the line varies with the purity of gold. By observing the color on the line, an experienced jeweler can tell the purity of gold. This method tends to get misused by pawn shop owners as the gullible customer does not know what is the purity of gold they have and they have to trust the pawn shop owner. In such cases, it is extremly easy for the pawn shop owner to lie about the actual purity of gold and pay less to the customer.
- This is a very simple, easy and quick method to test gold purity.
- This method to test gold purity is not very accurate;
- The person testing, needs to have a lot of experience in order to get a close approximation on the purity of gold.
2. Fire Assay Testing:
The method known as 'fire assay' is the oldest known method of testing gold and continues to be one of the most accurate. When gold is melted, a sample of the gold is taken, either by drilling through the poured bar or by capillary tube sampling while the gold is in a molten state. The sample is weighed very precisely and the weight recorded. All impurities and other metals are then extracted and removed, leaving pure gold. The weight of pure gold is compared to the previous weight of gold and its purity is calculated accordingly.
For example, if the weight of gold with purities is 10.000 grams and after removing other metals and impurities, if the weight of pure gold is 9.160 grams, in this case, the purity of gold will be 22 karat. Again, if the weight of pure gold is 7.500 grams, the purity of gold will then be 18 karat.
- Most accurate method of gold purity testing to date.
- The Fire Assay is destructive as it completely destroys the gold jewelry;
- This method is time consuming and can takes at least 30 minutes or more depending on the amount of gold.
3. X-RF Gold Testing (X-ray Fluorescence):
XRF is a widely-used, proven and accepted method to generate a complete analysis of gold samples, including purity and fineness.
How X-RF Gold Testing Works?
X-RF machines are able to determine results quickly as the X-ray assay takes only minutes to complete. This unique form of precious metal testing works by bathing the gold sample in X- rays. The metal then emits light (fluorescence) at an energy level specific to its atomic structure. By measuring this unique energy level, the X-RF machine accurately analyzes the purity of the sample. All the gold hallmarking centers in India which is controlled by the Government of India use this method to test and hallmark gold jewelry ornaments.
- This method measures percentages of ALL metals, not just gold;
- X-RF can be used to check the purity of any metal like silver or platinum for example;
- This form of gold purity testing is quick and easy;
- The X-RF machines are highly accurate in providing the exact karat weight and percentages of all elements within an item;
- The X-RF method to test gold purity is nondestructive.
- The X-RF machines to test gold purity is very expensive;
- The X-ray diode needs to be replaced every 2 years or so.
At Totaram Jewelers, we prefer the X-RF method the best . "With the volatility in the price of gold and other precious metals, we cannot afford the time or the potential inaccuracies of traditional gold testing methods to determine the value of items being bought or sold," says Raj Gupta, Owner of Totaram Jewelers, a retail online Indian gold and diamond jewelry store.