Dumortierite Quartz
Quartz var. Dumortierite (Dumortierite-bearing Quartz) · Decorative Stone and Semi-Precious Gemstone Specimen
Crystal System
Trigonal (Quartz), Orthorhombic (Dumortierite). Typically encountered as massive aggregates or tumbled stones polished into smooth shapes.
Mineral Group
Silicates (Subgroup: Tectosilicates for quartz and Nesosilicates for dumortierite)
Chemical Formula
SiO2 (host quartz) with Al7BO3(SiO4)3O3 (dumortierite inclusions)
Formation Process
Metamorphic and pegmatitic processes. Dumortierite forms as an accessory mineral in boron-rich aluminum-rich metamorphic rocks, regional metamorphic schists and gneisses, or granitic pegmatites, often later enclosed by crystallizing quartz.
About This Crystal
The specimen is a polished, elongated, rounded shape showing a vibrant, deep royal blue to indigo body color with characteristic dark blackish-blue webbed matrix lines and fractures. It has a smooth, glossy, polished surface with a waxy to vitreous luster and opaque to translucent transparency due to dense micro-inclusions of dumortierite needles within the quartz matrix.
Physical Characteristics
Color ranges from deep blue to violet-blue with dark inclusions. Streak is white. Cleavage is absent in quartz, distinct in dumortierite. Fracture is conchoidal to uneven. Specific gravity is approximately 2.65 for the quartz host. Tenacity is brittle.
Optical Properties
Singly refractive for isotropic aspects or doubly refractive uniaxial positive for the quartz host. Refractive index ranges from 1.544 to 1.553. Non-pleochroic in mass, though individual microscopic dumortierite crystals show strong dichroism.
Hardness & Durability
Origin Region
Notable sources include Madagascar, Brazil, Namibia, France, and the United States (Nevada). Forms in metamorphic and pegmatitic environments.
Hardness & Durability
Mohs hardness is 7 for the quartz host, making it durable and suitable for general jewelry use, though the embedded dumortierite can vary around 7 to 8. Good wearability with no easy cleavage planes to worry about.
Care & Maintenance
Clean with warm soapy water and a soft cloth. Avoid harsh chemical cleaners, prolonged exposure to extreme heat, and ultrasonic cleaners if internal fractures are present. Store separately from softer gemstones to prevent scratching.
Rarity & Value
Uncommon to Rare, depending on the intensity of the blue color and clarity of the quartz. High-quality royal blue material from Madagascar commands moderate to high collector prices. Usually untreated, though occasionally stabilized or dyed low-grade material might be found.
Special Characteristics
Vibrant natural blue coloration caused by microscopic fibrous inclusions of the mineral dumortierite trapped inside clear or milky quartz, creating a distinct denim-blue or royal-blue pattern.
Lore & History
Often referred to as the 'Stone of Patience' and associated with the throat and third-eye chakras. Historically used in crystal healing practices to enhance mental discipline, organizational abilities, and emotional stability. These are traditional beliefs and cultural symbolisms rather than scientifically proven claims.