Quantaflix  on Instagram: "Bismuth has a rhombohedral crystal structure that favors right-angled growth. When it cools from melt, the outer edges solidify first, leaving the inside molten. The molten core pushes outward, forming layered terraces. These terraces align at 90° angles, giving the square, stepped shapes. The rainbow colors come from a thin oxide layer causing light interference. These Bismuth crystals looks amazing."