Polyhedral 7-Die Gemini Dice Set - Purple-Steel with White by Chessex. Save 3 Off!. $9.67. Gemini dice were introduced in 2006 and were immediately very popular. Each dice has a beautiful blend of two base colors, making these dice a unique addition to any dice collection. This set contains one d20, one d12, two d10 (00-90 and 0-9), one d8, one d6, and one d4.