People are often mesmerized by the different colors, shapes, and sizes of sea glass, but what's most impressive is how it's made.
It's an incredible story, really--a story that begins long before a piece is ever spotted and plucked off a beach. The soft, soothing sand you love between your toes is made of rock and other hard materials broken down by wind and waves over time. When extreme heat is applied to that sand, it changes to a clear liquid-like substance that can be molded into items we use every day without much thought: cups, decorations, bottles, etc. Some of those items end up broken and/or discarded on the beaches of our oceans. Over time, the steady crash of the surf wears away the rough jagged edges and leaves a smooth, polished piece of glass. By the time you find these treasures in their awe-inspiring "gem" form, they may have been there for ten years, or a hundred, or more!
So what makes the different colors? Without getting too scientific, different colors of sea glass appear because glassmakers dye their glass different colors--sometimes for practical purposes, sometimes for decorative purposes. Plus, some colors are changed over time by natural chemical changes. As a result, some colors--like green and brown--are extremely common. Other colors--like lavender, cobalt, orange, and red--are super rare.