Gemology is the study of gemstones. A gemologist explains the gemstone’s physical and chemical makeup that makes it what it is. This includes the stone’s chemical formula, formation process, crystal structure, localities, hardness, specific gravity, refractive ability, and several other characteristics that are unique to every stone.
Find out all this and more about your favorite gemstones by selecting them from the list below.
Mohs Scale of Hardness
The Mohs Scale of Hardness is a universally accepted technique whereby the relative hardness of a stone is quantified by its resistance to scratches from another material. The higher the resistance, the harder the stone is considered to be. Typically, the Mohs Hardness Kit contains a sample of each mineral graduated according to the ten-point hardness scale. All values are estimations relative to other stones.
Broadly, Specific Gravity is defined as the ratio of a subject’s density/mass/weight/volume to a reference substance’s density/mass/weight/volume. In essence, it is a dimensionless measure. In gemology, it is the density of a particular gemstone as a ratio of the density of the same volume of water. Ideally, temperature and atmospheric pressure are also mentioned if it is different from the universally accepted “normal”.
Most gemstones are crystalline in nature, which means their atoms are arranged in a crystal form. Their crystal structure is determined by the unique setting of atoms within the crystal lattice. This structure determines the stone’s hardness, resistance, cleavage, electronic band structure, optical transparency and more. The crystal structure of a gemstone is identified using complex imagery techniques on an atomic level.
Theoretically, when a ray of light is incident on a non-opaque surface, it is reflected and refracted according to the specific characteristics of the surface without altering the velocity of light rays. However, in the case of certain anisotropic gemstones, when a ray of light is incident on the crystal lattice, it is split into two rays traveling at different velocities. Both the direction and the speed of light is altered by the crystal structure of the gemstone, a phenomenon popularly referred to as “birefringence” or double refraction.