Measuring gemstone density is one way of differentiating between two similar looking gems. For example, take a garnet and ruby. The two species may look alike, and two particular stones may even have the same dimensions. However, each has a unique density or specific gravity.
What is Density?
In case you forgot your high school science, density refers to how much mass something has per unit of volume. Or, think of density as the “compactness” of an item. For example, vegetable oil is less dense than vinegar. Thus, the oil floats on top of the vinegar and spices when a salad dressing separates.
Gemstone density or specific gravity are bulk properties independent of direction and typically uniform within a mass of material. Under ideal circumstances, two gems of the same species and variety have the same density. However, nature rarely obliges. In the real world, mineral density varies widely, even within a single crystal, due to impurities, cracks, and bubbles. Nevertheless, density is a useful parameter in gem identification. Therefore, you should understand these variable factors.
Specific gravity is the ratio expressing the weight of a given material compared to that of an equal volume …