While the most common image of beaches includes white sand and palm trees, beaches come in a rainbow of colors, from (almost) pure white to midnight black. That's because sand itself is the product of erosion, mainly of inland rocks or sea cliffs. As these rocks or cliffs weather over time—due to rain, wind, snow and other forces—particles are broken off and deposited on beaches via rivers or wind. Sand can also come from marine organisms, creatures whose shells or other hard parts are broken down by the ocean and deposited on the shore. Most light-colored beaches are made of quartz, but depending on what the rocks or cliffs surrounding a beach are made of, a beach can take on an entirely different hue.
Glass Beach—Kauai, Hawaii
It's not the sand that makes this Hawaiian beach so unique—it's the sea glass. On the southern shore of Kauai, near an industrial area, lays Glass Beach, whose shore is covered with a prismatic assortment of sea glass. The sea glass on Hawaii's beaches is distinct from sea glass elsewhere, especially compared to the eastern coast of the United States, because Hawaii's sea glass is often more round in shape (thanks in part to Hawaii's large waves) and contains more shades of blue than usually found elsewhere. Kauai's glass beach might be beautiful, but it owes its existence to a industrial garbage dump nearby—still, it takes the ocean decades (sometimes as long as 30 years) to transform broken bottles and other bits of trash into beautiful, smooth sea glass.