Book 27, Question 73
Why do grains of beach sand flash in the light?
Most beach and playground sand is full of quartz grains, which are tiny crystals with shiny faces.
When sunlight hits them, flat faces reflect light like tiny mirrors. Some sand also contains flakes of mica, which flash and shimmer. Sand can also hold bits of shell, rock, and volcanic glass, so every beach has its own mix. A magnifier shows a treasure chest.