Excellent: Outstanding and flawless in all dimensions. This quality is rarely seen in jewelry and is mostly acquired by collectors or long term investors.
Very Good: Above average in all dimensions with one or two minor flaws.
Good: Average quality with strengths and weaknesses.
Fair: Average quality with one or two obvious flaws.
Poor: Major imperfections.
Free of Inclusions: No inclusions are visible under a 10fold lens
Very Lightly Included: The trained eye perceives inclusions only with the lens and in some light conditions
Lightly Included: Only a 10fold lens reveals minor inclusions (not visible to the naked eye, often called "eye clean")
Moderately Included: Inclusions are visible to the unaided eye but do not harm the stones beauty (often called "nearly eye clean")
Heavily Included: Inclusions are obvious and influence the stones appearance (often called "included")
Excellent: Exactly the color everybody wants.
Very Good: Attractive and well saturated color. Suitable secondary hue.
Good: Fine main color but strong secondary hue. Off-color but charming
Fair: Off-Color in this variety, excessive or unsuitable secondary hue and/or much gray
Poor: Strongly washed out off-color
0-35 (Very Light to Light): Brightest hues. Bordering to colorless in the extreme (0). The appearance is dominated by luster and clarity, not color. Inclusions are very visible. Mostly desired in yellow, and partly pink.
35-60 (Light-Medium to Medium): Colors are not yet fully saturated but never too dark. Mostly desired in yellow, pink, green and partly blue
60-85 (Medium-Dark): Most varieties are wanted in these tones. Colors are fully developed but not overly dark. For luster to be lively the gem needs a good crystal and cut. Inclusions become less and less visible. Very desired in red, blue, purple and partly green
85-100 (Dark): Gemstones in deepest hue, bordering to black in the extreme (100)
Excellent: Innovative cut, especially beautiful and flawless in any dimension. A work of art.
Very Good: Flawless in any dimension.
Good: Flawless in all but one dimension (say, depth or symmetry)
Fair: Flawed in two dimensions (say, depth and symmetry)
Poor: Flawed in several dimension typically chipped and scratched surfaces