Much like a diamond, the various combinations of a stone's cut, colour, clarity, and carat weight, along with availability and accessibility, determine rarity. You will find a brief description of those features here. These explanations are based on the system for gemstone evaluation established by the Gemmological Institute of America (GIA).
Colour is the most defining characteristic of a gemstone. Most gemstones occur in a spectrum of colours, while some have more restricted palettes. Since the colour phenomenon in gems is very complex, experts analyse the chromatic options in terms of three essential components: hue, tone, and saturation. Hue is the basic or the primary colour of the gemstone, tone refers to the lightness or darkness of the colour and saturation refers to the purity or intensity of the primary colour.
As a general rule, a bright, intense, pure, rich and vivid colour is always best. The most valuable gemstones are those that exhibit a pure colour with only slight hues of other colours in addition to their primary colour.
The primary colour should be medium, neither too dark nor too light.
While buying gemstones you need to be aware of colour ranges and objective value assessments, but it’s best to rely on your eyes and heart. Select your gemstone by trusting your instincts; if a particular colour speaks to you, by all means listen!