Guide Gemstone Density
Different types of gemstones vary in density, and this fact is of interest to both gemologists and consumers.
It is important for consumers to understand gemstone density because buying colored gems by carat weight alone can lead to unexpected results. Though it is common to buy diamonds by weight, colored gems vary greatly by density. For example, a 1 carat sapphire is significantly smaller than a 1 carat diamond, while a 1 carat opal is significantly larger.
In gemology, the density or specific gravity of a gemstone is computed as the ratio of the density of the material to the density of water. The density is expressed as a number which indicates how much heavier the gemstone is compared to an equal volume of water.
Most gemstone varieties are 2 to 4 times denser than a equal volume of water. But the range is quite wide -- from 8 for cinnabar to 1 for amber. Diamond, at 3.50 to 3.53, falls approximately in the middle.