October Birthstone: Opal

October has the privilege of two birthstones: tourmaline & opal. Today, we’re focusing on opals, which are the more traditional of the two. Opals are formed in fissures of pretty much any rock, but most commonly limonite, sandstone, rhyolite, marl and basalt. It’s a mineral gem deposit that forms at relatively low temperatures, and it’s internal structure is what gives opal its trademark technicolor beauty.

The tiny silica spheres refract light from one end of the visible spectrum to the other, and opals themselves come in a huge variety of colors, depending on the formation conditions. Black and red opals are the most rare, while white opals are the most common – but no less beautiful! Here are some of our favorites.