There are many places where one would be able to purchase diamond color scales. One would be able to purchase this product from shopping websites such as Amazon or eBay.
These letters -- G and H -- are used to describe a diamond as 'near colourless'. You can review them on the scale of diamond colour, below.
"fcly" is not a commonly recognized term in diamond color grading. The standard diamond color grading scale ranges from D (colorless) to Z (light yellow or brown). If you have more context or information, I can try to provide a more accurate answer.
You can read from the chart, below, and learn where G and H fall in the diamond colour range.A "G H" colored diamond means that it is in the near-colorless range on the color scale. The diamond color scale was developed by GIA (the Gemological Institute of America) in the mid 1900s. Before GIA developed this scale, there was no universal way of grading diamonds, so diamond grades ended up being widely varied and confusing. The diamond scale starts at "D", meaning that it is completely colorless, and extends to "Z" meaning that the diamond is extremely saturated with color (can be either yellow or brown--the hue doesn't matter). Diamonds in this color and beyond are considered to be "fancy" colors based on colour saturation.Face up, the general population won't be able to tell the difference between a "G" and "H" colored diamond. In a setting, they will look white, unless you put the diamond in a yellow gold setting; in this case, the yellow hue from the ring will be reflected into the diamond, causing the diamond to seem tinted yellow.Most people stick in the "G H" color range because you can get more "bang for your buck."
A diamond is the hardest natural substance, scoring a 10 on the Mohs scale. It has a brilliant luster due to its high refractive index. The streak color of a diamond is colorless, as it does not leave a streak on a streak plate.
Diamond is the top of the Mohs hardness scale, ranked at 10.
The 4 C's of diamond grading include the carat weight, cut, color and clarity. When one decides to buy a 4 C's diamond, one should consider the cut of the diamond, which is how the diamond appears in terms of proportions and brightness.
On the Mohs scale of relative mineral hardness, diamond is the hardest at 10.
Diamond, with a hardness of 10 on the Mohs scale.
In the scale of 'white' diamonds, the designation E is in the high end of 'colourless', meaning that the diamond's colour characteristic is highly desirable. You can read more about the 'shades of white' in 'white' diamonds, below.
It is dia mond . . . diamond. On the scale from 1 to 10, diamond is the hardest at 10.
The term "SI" indicates a clarity category, not a colour category. For clarity, "SI" indicates slightly included, and is usually followed by a number, 1, 2, or 3. In this scale, fewer is better.
You can get a diamond color enhanced through coating or polishing.