Turquoise
Turquoise (IMA approved species name: Turquoise) · Semi-Precious Gemstone
Crystal System
Triclinic; typically forms in massive, cryptocrystalline, or botryoidal habits rather than visible crystals.
Mineral Group
Phosphates; Turquoise group
Chemical Formula
CuAl6(PO4)4(OH)8·4H2O (Hydrated copper and aluminum phosphate)
Formation Process
Secondary/Sedimentary process; forms by the percolation of meteoric water through copper-bearing weathered rocks in arid environments, typically in volcanic or sedimentary host rocks.
About This Crystal
This specimen is a polished heart-shaped cabochon displaying a vibrant robin's egg blue to greenish-blue hue. It is opaque with a waxy to sub-vitreous luster. It features a distinctive matrix of brown and tan host rock inclusions.
Physical Characteristics
Color: Sky blue to apple green; Streak: White to greenish-white; Cleavage: Perfect (rarely seen in massive forms); Fracture: Conchoidal to uneven; Specific Gravity: 2.6-2.9; Fluorescence: Weak greenish-yellow or blue under longwave UV.
Optical Properties
Refractive Index: 1.610-1.650; Birefringence: 0.040 (not visible in massive form); Pleochroism: Weak; Opaque; No significant dispersion or fire.
Hardness & Durability
Origin Region
Notable sources include Iran (Nishapur), Southwestern USA (Arizona, Nevada), China (Hubei), and Egypt (Sinai Peninsula).
Hardness & Durability
Mohs Hardness: 5 to 6; Toughness: Fair to good (brittle if dehydrated); Porous nature makes it susceptible to staining and chemical damage.
Care & Maintenance
Clean only with warm, soapy water; avoid ultrasonic or steam cleaners. Store away from heat and direct sunlight to prevent fading. Avoid contact with perfumes, oils, and household chemicals due to high porosity.
Rarity & Value
Range from common to rare; value is driven by color (saturated 'Persian blue' is highest), lack of matrix, and origin. Common treatments include stabilization (plastic impregnation), dyeing, and reconstitution.
Special Characteristics
Features a 'matrix' (web-like patterns of host rock); cryptocrystalline structure gives it its unique waxy luster; some specimens may show a slight color change over decades due to skin oil absorption.
Lore & History
One of the oldest gemstones in history; used by Ancient Egyptians (since 3000 BCE), Aztecs, and Native Americans. Symbolizes protection, wisdom, and good fortune; traditionally associated with the Throat Chakra.