No, we are not talking about the attracting forces of planets in the solar system, but a very accurate method of determining just what type of metal that ring, necklace, watch fob, token, etc... is made of.

Specific gravity is the ratio at which a material displaces water in relation to its bulk.

The formula for the specific gravity of any material is:

aw = air weight (weight of object in air)

ww = water weight (weight of object in water)

This is an extremely delicate test. If it is not performed exactly, you will not get correct results. On the other hand, its accuracy when properly done, is far superior to that of almost all other methods of testing.

The one piece of equipment you will need is a scale calibrated in grams. If it is calibrated higher than grams it will not work. You can find specific gravity scales at Mineral & Mining Supply Dealers from between $15 to $75 or you can convert an ordinary “pan scale”.

To convert the pan scale, remove the pan and tie a length of thin nylon string to the extreme edge of the pan holder. The string must not be long enough to touch the bottom of whatever the scale is sitting on.

Next, you will need a glass tumbler filled 3/4 full with water to be placed below the string. When the item is tied to the string and placed in the water it must not touch the sides or bottom of the tumbler.

Weigh the item before you put it in the water (writing down your results) and then weigh it in the water. Lets look at an example. A gold ring.

Weight in water 55.5 Grams

Weight in air 60.0 Grams

Subtract water weight from air weight (4.5 Grams)

Divide the “loss of weight” into air weight.

60.0 divided by 4.5 = 13.33

13.33 is the specific gravity of the material the ring is made of.

Now comes the time when you will need a table of the specific gravity for different materials. Following is such a table for most of the metals we detectorists are interested in.

In our example you can see that our ring is most likely 14K. The more accuracy you can get from your scale the closer you can get to the materials specific gravity in the table.

If you need additional specific gravities, you can find them at the local library. Every material, not just metals, has a specific gravity so this test works for gem stones and all other natural elements.