Those pretty colors are all about light and structure, not pigments. In an opal, tiny glass‑sized silica spheres are packed in a regular lattice. When sunlight hits them, the light waves bounce off adjacent spheres and interfere. Depending on the spacing, certain wavelengths are reinforced—hence the rainbow flash. Labradorite works a bit differently. It’s a feldspar with a bit of iron and some internal micro‑fractures. Those fractures create tiny prisms that refract and disperse light, giving that shifting, sea‑foam look. Both are nature’s own diffraction grating, turning ordinary light into a storytelling palette. If you could pick up one of those stones, you’d feel like you’re holding a piece of the planet’s own kaleidoscope.

Yes, the spacing is key. If the spheres are closer together the interference peaks shift toward shorter wavelengths—more blue or violet. If they’re further apart, the peak moves to the red end. That’s why a single opal can have a range of colors; as the light angle changes, the path difference changes and you see a different color. If you could tweak the silica packing—maybe by controlling the cooling rate of a silica gel or adding a small amount of polymer—you could set the lattice spacing and lock in a particular color. It’s a delicate balance, but the idea of engineering a custom rainbow stone is a fascinating experiment in natural photonics.