This is "parasitic growth." Dust fell in, or the solution cooled too fast, creating spontaneous nucleation.
There is something deeply satisfying about watching a cluster of jagged, sparkling gems emerge from a simple jar of liquid. DIY crystal growing is the perfect intersection of a rainy-day craft and a serious chemistry lesson. Whether you are looking for a weekend project with the kids or want to create custom home decor, growing your own crystals is surprisingly easy—and addictive. diy crystal growing
As your crystal grows, move it to fresh solutions with different food colorings every few days. Layers of color will form inside the crystal. This is "parasitic growth