Rainbow quartz crystal has rainbows inside due to fractures. 

Rainbow quartz crystal is optimistic and happy. They remind us that we are loved and they remind us to look for the gifts our traumas bring us.

Sometimes Rainbows appear on the surface between two closely connected (fused) crystals.

Metaphorically, this can represent how a relationship with a closely-attached-other can bring us Rainbows. Often the fusing of the two crystals produces a surface on which Rainbows like to ride. The relationship with the closely-attached-other creates a Rainbow to be explored and honored while the two are connected.