As a silver buyer this is important to remember silver metal is expensive relative to most other metals therefore there is always an economic incentive to pass lower content silver as higher content silver. Hence, remember to test for silver purity.
Silver is only weakly magnetic. If in the presence of a magnet it sticks strongly, then it is likely to have a iron (ferromagnetic) core. Only use this test in conjunction with other tests as the item may have a core which is not made of iron.
There is variant of this test for bullion bars, called the sliding test, where you use a strong magnet and slide it down a bar at forty-five (45) degree angle. As silver is weakly magnetic, it should cause a "braking effect", so it should slide slowly relative to an equivalent non-magnetic item.
Silver has a very high thermal conductivity. When a piece of ice is placed on silver bullion it should begin to melt immediately as the temperature of the bullion is transferring to the ice very quickly. This test is mainly only practical for silver bullion not silver jewelry.
Silver coins when tapped should make a distinguishable bell-like sound.
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 silver testing kit will have one or more bottles of acid. There will be instructions with each specific test to indicate what color change to expect for what purity of silver. Note the scale of the test is applicable for (the minimum % silver the test works for) and also note that the acid in the test typically has a relatively short shelf-life.
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.
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)
Other equipment that is common in silver 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.
- Diamond tester for confirming a precious stone is a genuine diamond (or moissanite).