Diamond dust refers to tiny ice crystals that form in extremely cold conditions, often seen in polar regions or during winter. These crystals can create a shimmering effect in the air, resembling sparkling diamonds when sunlight hits them. This phenomenon typically occurs when the temperature drops below freezing, and moisture in the air condenses and freezes. Unlike snow, diamond dust is light and can float, creating a beautiful visual display without accumulating on the ground. It is most commonly observed during clear, calm nights in winter.