Opal

gemstones · silica · rainbows · minerals

Made of water and rock. Opal is not a true crystal like diamonds are. Instead, it is a mix of silica (the same stuff that makes sand) and water that gets squeezed together at low temperatures deep in the earth.

Rainbow light trap. Opal's special jumbled structure acts like millions of tiny mirrors that bounce light around inside the stone, creating those amazing rainbow flashes and color changes you see.

Wet gemstone. Unlike most gemstones that are dry, opals are actually about 6 to 10 percent water inside. This water is what makes them so fragile and why they can crack if they dry out too much.

Found in cracks. Opals form in cracks and gaps in rocks over millions of years, usually nestling inside sandstone, basalt, or other common rocks near minerals like limonite.

Everywhere underground. You can find opals hiding in almost any type of rock around the world, but they love certain rocks like rhyolite and marl the most.