KARAT: Karat is a measure of the fineness, or purity, of gold. 24K is pure gold, 18K is 75% gold and 14K is 58%.

CARAT: Carat is a weight measurement for gemstones. 1 carat equals .2 grams (metric).

MINERAL: A mineral is a homogeneous substance formed in the earth’s crust by inorganic forces, whose chemical and physical properties are constant within narrow limits. Most gemstones are minerals, but most minerals are not gemstones.

FACET: A facet is a flat surface on a gemstone.

CABOCHON: A cabochon is a gemstone having a curved or domed surface, used mostly for opaque gems and those with phenomena such as chatoyancy or asterism.

ASTERISM: The effect that causes a star on the surface of a gemstone.

CHATOYANCY: The effect that creates a cat’s eye line of light across the surface of a gemstone.

FLUORESCENCE: A form of luminescence can be stimulated in some gemstones by the application of long or short wave ultraviolet light.

SYNTHETIC GEMSTONE: A synthetic gemstone is a man made gemstone that has the same physical and chemical properties as the naturally occurring gemstone.

SIMULANT: A stimulant is a simulated gemstone that can be natural or synthetic. It looks like the gemstone it simulates but does not have the same properties, and is not the same mineral.

INCLUSIONS: Inclusions are features contained within a gemstone -- often called "flaws." These can be formed before, during or after the crystal growth of the gemstone. The number, size, and location of inclusions sets the clarity grades in gemstones.

CLARITY; Clarity is a classification term in the grading of polished, transparent gemstones which denotes the degree of freedom from inclusions in the gemstone.

CLEAVAGE ; Cleavage is a property possessed by some crystalline minerals which enables them to divide along a plane of weaker molecular bonding.

REFRACTION; Refraction is the bending of light rays as they pass through the interface of media (in this case minerals) having different optical densities.

ENHANCEMENT; Enhancement is the improvement of either the color, the clarity, or both of a gemstone using technology and techniques.

If you have any specific gemstone questions please feel free to call me at William’s Jewelers. I’d be happy to help clear things up any way I can.

Matt Dendel
Gemologist, GIA