Turquoise is an opaque, blue-to-green gemstone, a hydrated phosphate of copper and aluminum, prized for millennia in jewelry and admired for its color and perceived spiritual properties, used by ancient Egyptians, Aztecs, and Native Americans as a symbol of protection, luck, and connection to the spiritual world, with its hardness around 5.5-6.5 on the Mohs scale, making it relatively soft and porous. Its appearance ranges from sky-blue to greenish, often with dark or brown veining (matrix), and its value varies by color saturation, origin (like Kingman, Sleeping Beauty), and presence of matrix, with Spiderweb matrix being particularly prized.