Specific gravity is the weight in grams of one cubic centimeter of a metal.
The Specific Gravity Test is used to calculate the gold content of gold nuggets that contain a mixture of gold and other materials. In this example of the specific gravity test, we use gold mixed with quartz. Simply put, the formula is 3.1 x the weight in water, minus 1.9 x the weight in air:
Wet nugget weighs 74.5 grams x 3.1 = 230.95
Dry nugget weighs 96 grams x 1.9 = 182.4
230.95 - 182.4 = 48.55
31.1 = number of grams per ounce
48.55 / 31.1 = 1.56 ounces of gold
Original dry weight = 96 grams / 31.1 = 3.08 ounces.
Subtract the difference between the wet and the dry:
3.08 ounces - 1.56 ounces = 1.52 ounces.
Therefore what is left is 1.52 ounces of quartz.
"Wet" = weight in water - Put container of water (enough water to cover nugget) on scale. Tare (zero) out scale. Hang nugget by string in water. Note weight.
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.
|Metal||Symbol||Specific Gravity||Melting Point (° F)||Melting Point (° C)|
Pure gold has a density of 19.32 gm/cm3 while 14K gold has a density between 12.9 and 14.6 gm/cm3, depending upon the composition of the alloy.