Gem Stacker, also known as Gem Stack, gives a player the ability to see how much money they can make by selling gemstones that they personally prepare from uncut rock. The game features a hand that floats above a conveyor-style racetrack. The player uses the hand, which races forward once gameplay commences, to grab, stack and refine the materials needed to make cut gems and jewelry.
The game starts with rocks that the player must collect with the hand in a long stack in front of them. They must run the rocks through an automated rock-cracking machine to reveal the raw, uncut gemstone, which they then cut, polish, swap and refine in other ways. Once they have finished products, they access a shop area where they can sell them to earn money. Depending on the amount they make from the sales, they achieve a certain professional level on a vertical board that looks like the tower board of a carnival strongman game. When they finish a level, they win extra money and sometimes receive treasure, such as a piece of jewelry or new type of hand.
With each new level, the number of shops and sales opportunities increase, and the player receives access to more refinement and jewelry options, such as golden hooks to make pierced earrings. They eventually receive access to a certificate of authenticity option that verifies if their gems are fake or real and increases their sales potential.
Gem Stacker doesn't make any part of the process easy. It sets up obstacles on the racetrack, including rock crushers that can destroy cut gems, circular saws and a thief.