Turquoise
Turquoise · Semi-Precious Gemstone / Decorative Stone
Crystal System
Triclinic, commonly found in microcrystalline, massive, or botryoidal habits
Mineral Group
Phosphates, specifically an hydrous phosphate of copper and aluminum
Chemical Formula
CuAl6(PO4)4(OH)8·4H2O
Formation Process
Secondary origin, formed by hydrothermal leaching and supergene weathering of pre-existing copper and aluminum-bearing rocks in arid climates at shallow depths.
About This Crystal
An oval-shaped, polished cabochon displaying a light robin's-egg blue to pale greenish-blue body color, prominently intersected by brownish-tan matrix webbing (host rock inclusions of limonite or sandstone). The luster is waxy to sub-vitreous and the transparency is opaque.
Physical Characteristics
Color ranges from sky blue to green-blue with white, brown, or black matrix veins. Streak is white to pale greenish-white. Cleavage is good in one direction and fair in another, but rarely seen in cut stones. Fracture is conchoidal to uneven. Specific gravity is 2.60 to 2.85. Tenacity is brittle. Can exhibit weak green or yellow fluorescence under shortwave UV light.
Optical Properties
Biaxial positive with refractive indices around 1.61 to 1.65. Displays weak double refraction. Pleochroism is generally weak to nonexistent due to the massive, microcrystalline nature. No chatoyancy or asterism, but distinctive webbed patterns (matrix) are common.
Hardness & Durability
Origin Region
Notable sources include the Southwestern United States (Arizona, Nevada, New Mexico), Iran, China, Egypt (Sinai Peninsula), and Mexico. Forms in arid regions where acidic groundwater reacts with copper-bearing minerals.
Hardness & Durability
Mohs hardness is 5 to 6. Toughness is fair to poor, making it somewhat porous. Moderate stability; sensitive to heat, acids, skin oils, and household chemicals, which can cause the blue color to turn green or fade over time.
Care & Maintenance
Clean gently with warm, soapy water and a soft cloth. Never use ultrasonic or steam cleaners, harsh chemicals, or abrasive materials. Store separately in a soft pouch away from direct sunlight and harder gems to prevent scratching and dehydration of the stone.
Rarity & Value
Uncommon to Rare depending on grade, natural clarity, and geographic origin (such as vintage American spiderweb turquoise). Value is determined by color intensity (Robin's egg blue is most prized), minimal matrix vs. aesthetic matrix webbing, lack of stabilization treatments, and size. Price ranges widely from affordable commercial grades to high collector values for pristine natural Persian or Bisbee turquoise.
Special Characteristics
Often features intricate spiderweb or butterfly matrix patterns caused by host rock inclusions. Many commercial turquoise stones undergo stabilization (impregnated with plastic or resin) or enhancement (waxing or color-tinting) to improve durability and color retention.
Lore & History
Turquoise is one of the world's most ancient gem materials, revered by ancient civilizations including the Egyptians, Native Americans, Persians, and Aztecs as a sacred stone of protection, good fortune, and healing. Historically used in burial amulets, royal jewelry, and ceremonial weapons. In modern crystal healing and metaphysical practices, it is traditionally associated with the Throat Chakra, believed to promote spiritual grounding, communication, and emotional balance, though these are cultural traditions rather than scientifically validated properties.