Druzy stones are beds of tiny crystals that formed inside cavities in rocks such as agates. Called drusa in Brazil, they are often a type of quartz, but can also be made of other minerals such as garnets, calcite, dolomite and malachite. They come in many colours, due to the different minerals inside the rock, from clear or snowy crystals to deep reds, greens, browns and blues. The surface can also be coated with titanium or gold to produce a dazzling metallic effect. Druzy quartz gems take millions of years to form, starting as bubbles of gas inside molten rock below the earth’s surface. As the rock cools and hardens, the crystals begin to grow on the inside of the cavity, taking their colours from elements like iron and cobalt that collect on the wall of the hidden space. When the rock is split open, the magical display of minerals is revealed.