Ohaus Scales

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.

 

Specific Gravities of Common Metals

 

Metal	Symbol	Specific Gravity	Melting Point (° F)	Melting Point (° C)
Copper	Cu	8.96	1981	1083
Gold	Au	19.32	1945	1063
Iron	Fe	7.87	2802	1539
Lead	Pb	11.34	621	327
Nickel	Ni	8.90	2651	1455
Palladium	Pd	12.00	2831	1555
Platinum	Pt	21.45	3224	1773
Silver	Ag	10.49	1761	961

 

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.