Possible Clues:

• Swirly-colored marbles
• Minnesota's state gemstones
• Stones like to include entrance
• Collectible marbles
• Article on theatre with small version of The Stones
• When jamming opening, 29-fillers required
• A movable barrier in front of small gemstones
• Ancient May birthstones
• Which journalist's novels and reviews were little gems?
• Patterned marbles