How are gemstones formed naturally?

Natural gemstones form over millions of years, through geological processes that involve intense heat and pressure, plus the mixing and interaction of mineral-rich fluids, deep in the Earth’s crust or even in the mantle.

In the end, the geological setting controls what gem appears. With igneous activity, crystals like diamonds and peridot form straight from cooling magma. Metamorphic conditions add high heat and pressure and they reshape older rock frameworks, which leads to rubies and sapphires. Meanwhile, sedimentary processes work differently, because water will place minerals into tiny cracks and empty spaces, over long time periods, and that’s how opal, turquoise and malachite form.