There are 8 gem colors in the game: Gold, Emerald, Moonstone, Pearl, Amethyst, Ruby, Topaz, and Sapphire. They are each represented 7 times. This is possible because Kings (typically the weakest Gin Rummy card) have two gems each, adding 4 more gems slots, so all together there are 52 cards, but 56 gem slots. (56 slots / 8 gems = 7 each). Kings now can participate in one of two Stashes; Stash is a new meld in Gem Rummy; it is a group of at least 4 cards all of the same gem.
Every 8 cards starting with Aces and going up, has all 8 gems represented. In other words Aces and Deuces will have all 8 gems, and so will 3's and 4's, etc.
Since the King now has two colors/gems it is not as weak as before (as in original Gin Rummy). Also since the Queens can be used in a special meld called "Queen's Diamonds" they have also been strengthened. This creates a better balance for high and low cards. By association with Queens and Kings (since they both will be held more often now), Jacks and 10's also get a bump in action as far as Runs go, and therefore 9's as a result, and so on. Typically Aces and 2's are the strongest cards in traditional Gin Rummy because of their low values allowing one to "Knock" and end the hand.
Although Jokers are not used in hands, they are still laid out to hold the dice roll (Red Joker) and they have other useful info. like the names of the gems and the official website address.
Three other deviations from Gin Rummy are that 11 cards are dealt to each player instead of 10, and there is also a "Minimum score of 11 points" that are earned by the Knocker as long as she/he is not Undercut. "GEM PARTS" is a bonus that can be earned (not a meld) when a player has "all 8 gems anywhere in their hand at the end of a hand". GEM PARTS is easy to locate in hand because each letter of the words "G-E-M P-A-R-T-S" is represented by the first letter of each gem, and these letters are also on the cards along with the gem symbol.
Gem Rummy operates much like the Oklahoma variant of Gin Rummy with respect to the "Knock" number. Since a dice roll of 2d6 determines the Knock number in Gem Rummy, we have a range of 2-12 with 6, 7, or 8 being very common. This is similar to Oklahoma Gin Rummy where 2-10 is the range with average near 7. In Oklahoma Gin Rummy a card from another deck is pulled to represent the Knock number and if an Ace is pulled usually "Gin" is required to go out ("0" count); any face card nets a Knock number of "10" in Oklahoma Gin Rummy. Standard Gin Rummy always uses "10" as the Knock number.