Volcano Agate Anatomical Human Heart Carving *UV Reactive* | High Quality | UV Reactive | Blacklight | Heart | Home Decor | Quartz | Halloween | Oddities | Goth Decor | Skull decor 3.1” x 2.1”. 223 grams A must have for your UV collection! Volcano agate is a type of chalcedony that forms when lava and groundwater interact. It's also known as volcanic or lava agate. It's formed when Lava containing UV-reactive minerals flows and traps gas bubbles, the lava hardens into rock, water flows through the gas cavities, transporting silica. Silica crystallizes on the gas bubbles to form agate. When exposed to longwave UV light, it glows a bright green color. The amount of uranium in the chalcedony determines how strongly it reacts to UV light You will receive the exact item listed. Gemstones and crystals are natural products of Earth. Stones and crystals may have slight blemishes and imperfections. Please review the measurements and view all the photos before making a purchase.