"Diamond Mine" is a simple falling-shapes type puzzle game. You move the gems to make rows or columns of three or more which then disappear, dropping the ones above them into position. The game, made by Pop Cap Games, has been around since at least 2005, both with this name and (marketed by Microsoft) as "Bejeweled." Except for the names, they are identical. The only real "cheats" are a set of codes to allow you access to higher levels of the game without going through the earlier ones.
Reach Levels 6 through 10 by typing in "RKS." Inputting the code "QEZ" gives you access to Levels 11 through 15.
To jump to Levels 16 through 20, use the code "GEM." Levels 21 through 25 can be accessed directly by using the "WTH" code.
To access Levels 26 to 30 without playing through, type in "EME." "FUN" will get you to the top five levels--31 through 35.
Old Gems for New
There is a second, more advanced version of the game, called "Bejeweled 2 Deluxe," which has the original "Diamond Mine"/"Bejeweled" game embedded in it. If you are playing on a PC, type the code "oldskool" at any time to render the jewels like the original "Diamond Mine"/"Bejeweled" gems.
Getting to the original mode
A somewhat more complicated procedure will get you into the full original game, which is different from the "Bejeweled 2 Deluxe version" primarily in not having Power Gems or Hyper Cubes. To play the original "Diamond Mine," you need to use your mouse to circle the four "Mode Select" buttons with the cursor in a set order and direction. Just touching the buttons in order won't do. Circle "Classic," "Action," "Endless" and "Puzzle" buttons in that order, always circling each button in a clockwise direction. It might not work the first or even the second time, so keep trying until the original game version starts.