This is a "stat plus stat" addition table that lists all Northrend gems:
If you take the numbers from the column header and add the row header, you get the actual stats of the gems.
The background colors are the stat colors in the headers and the gem colors in the table.
The table also shows how the different cuts are called (the adjectives). If you associate the adjective of a cut with the name of the right material, you get the full name of the gem.
Also, mousing over a gem will show it's description.
Northrend perfect uncommon gem. (When cut, an uncommon northrend gem has a chance to be perfect through the [Gem Perfection] ability. Perfect uncommon gems are between uncommon and rare in quality (except for Mp5).
Jewelcrafter-only [Dragon's Eye] gem. These are made by jewelcrafters for themselves, they always provide a single stat (they are on the diagonal) and they are 70% better than the epic gem associated (Mp5 is 100% better).
This indicates that the stat value of a gem is one point greater than the expected result from the addition. (Exemple: [Runed Scarlet Ruby] should have 9 + 9 spell power = 18. However it has 19.)
↓
This indicates that the stat value of a gem is one point less than the expected result from the addition.
