Possible Clues:

• Triangular pyramids
• Heartbroken to block dubious trade in pyramids
• Four-sided dice, e.g. (Note the last 3 letters of this answer + the start of 34-Down)
• Strange three-D art beginning with abstract geometric figures
• 'D4' dice in role-playing games, e.g
• Some pyramids, though not the ones at Giza
• Four-sided dice, for example
• Pyramids built of earth rated fantastic
• Broken-hearted over upside-down painting's shapes
• These are solid, hard rocks round back of cove behind swimmer