Gemstones are a product of the earth. Some, like diamond and zircon, were formed deep in the earth and brought to the surface by explosions of molten rock. Many, like topaz, tourmaline and aquamarine, crystallised slowly from hot fluids and gases as they cooled and solidified, far below the surface of the earth. Others formed from liquids filtered into cracks and pockets in rock, like Australian opal. Some, like garnet and jade, formed when rocks were heated and pressurised by earth movements, and recombined to form new, different minerals.
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