Turquoise: it is a Hydroxyphosphate of Copper and Aluminum Hydrate responding to the formula (CuAl6[(OH)2|PO4]4H2O). Crystal system: Triclinic in rare prismatic crystals. It occurs mostly in massive form of Cryptocrystalline Aggregate. Luster: glassy to waxy. Transparency: opaque. Color: light blue, green, light greenish blue. It is sometimes found in association with other Copper minerals, such as Chrysocolla and Malachite. Mohs hardness: 5–6. Density: from 2.60 to 2.90 g/cm3. Refractive Indexes n = 1.610–1.650, at the refractometer only one measurement at 1.61/1.62 is possible.
