People value gemstones for all sorts of reasons.
They're usually rare, pretty durable, and most of all, they're shiny and sparkly.
They can have multiple colors, streaks of light, weird inside-out shapes, and all kinds of other qualities.
The things we consider gemstones are often made up of minerals arranged into different types of crystals, although a few are made up of molecules that are arranged totally randomly.
But either way, their properties come from their specific chemical structure.
At the atomic level, it's simple geometry.
But it leads to some of the most beautiful natural materials on Earth.
When you look at a gemstone, probably the first thing you notice is its color.
Some gems, like tourmaline and fluorite, can come in practically any color you can think of.
And often, those colors come from transition metals that are incorporated into the mineral's crystal structure — metals like copper, iron, and zinc.
