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  • Specific Gravity


    This can get very technical but essentially specific gravity is a number that determines the average density of the item

    being tested. it can then be matched up to a table to determine the purity of possible gold and silver content.

    fine Gold has a specific gravity of 19.3 and fine silver 10.49.
    These numbers are also known as densities measured grams per cubic centimeter.

    Many stackers are concerned about fakes.
    Having confirmed weights and dimensions another test is to make a specific gravity test.
    Sometimes measuring coin thickness relies on averages - centre thickness, rim thickness etc and some wear and tear perhaps so to eliminate doubt make another measurement - the SG test.

    One quick way to measure SG is to use precise electronic scales and follow these steps -
    1. Weigh your coin in grams e.g. 31.2g
    2. Place a paper ( or lightweight ) cup on the scales and fill half full with cold water.
    3. Tare i.e. zero the scales
    4. Support your coin in a cradle ( cross ) of very fine thread and dip it into the water ensuring it is completely submerged AND not touching the bottom.
    5. Read the scales e.g. 2.97g
    6. The ratio of 31.2 / 2.97 = 10.5 confirming silver






    10.4 to 10.6








    10.9 to 12.7


    12.9 to 14.6

    18ct Yellow

    15.2 to 15.9

    18ct White

    14.7 to 16.9


    17.7 to 17.8

    Sterling Silver

    10.2 to 10.3

    950 Platinum



    This gets a tad more complicated with say a gold sovereign.
    You need to work out ratios knowing that the gold content is 22/24 and the other part 2/24 is either silver or copper.

    whilst the sg test works well for silver due to it's relative low value and the

    possible cost of ensuring a counterfeit passes this test. it's different for

    gold which has a close density replacement in the form of tungsten(sg 19.6).

    thus the sg test alone should not confirm gold on larger pieces where

    drilling and tungsten filling is known to exist.

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