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Specific Gravity

What is specific gravity? Specific gravity is simply the weight in grams of one cubic centimeter of a metal.

The Specific Gravity Test is used to determine the amount of gold in a nuggets that contain a mixture of gold and other materials.

In this example of the specific gravity test, we are using a gold nugget mixed with quartz. Simply put, the formula is 3.1 x the weight in water, minus 1.9 x the weight in air:

Dry nugget weighs 96 grams x 1.9 = 182.4

"Wet" nugget weighs 74.5 grams x 3.1 = 230.95

  • "Wet" = weight in water - Put a container with enough water to cover the nugget on a scale. Tare (zero) out the scale and hang the nugget by a string in the water.

Subtract the dry weight from the wet weight
230.95 - 182.4 = 48.55

Now we devide 48.55 by 31.1 to determine how much gold is in our nugget
48.55 / 31.1 = 1.56 ounces of gold

  • 31.1 = This is the number of grams per ounce of gold

Original dry weight = 96 grams / 31.1 = 3.08 ounces.
Subtract the gold weight from the dry weight.
3.08 ounces - 1.56 ounces = 1.52 ounces.
Therefore what is left is 1.52 ounces of quartz.

The specific gravity for gold is 19.3.
The specific gravity for quartz is 2.65.
The ratio between gold and quartz is 7.28 X.

 

Here are specific gravity’s and other properties of a few more metals:

Metal

Specific Gravity

Melting Point (ºF)

Melting Point (ºC)

Copper

8.96

1981

1083

Gold

19.32

1945

1063

Iron

7.87

2802

1539

Lead

11.34

621

327

Nickel

8.90

2651

1455

Palladium

12.00

2831

1555

Platinum

21.45

3224

1773

Silver

10.49

1761

961