Brown Tourmaline
Dravite (Tourmaline Group) · Semi-Precious Gemstone / Mineral Specimen
Crystal System
Trigonal; typically occurs as elongated prismatic crystals with vertical striations or massive/granular aggregates.
Mineral Group
Silicates (Cyclosilicate)
Chemical Formula
NaMg3Al6(Si6O18)(BO3)3(OH)3(OH)
Formation Process
Metamorphic or Magmatic; typically forms in aluminum-rich metamorphic rocks (schists) or through hydrothermal processes in pegmatites.
About This Crystal
Opaque to translucent dark brown to brownish-black specimen with an earthy, weathered surface. Shows a granular to massive texture with a vitreous to resinous luster on fresh breaks.
Physical Characteristics
Color: Dark brown to black; Streak: White to light brown; Fracture: Conchoidal to uneven; Specific Gravity: 3.03 to 3.10; Tenacity: Brittle.
Optical Properties
Refractive Index: 1.614 - 1.666; Doubly refractive (uniaxial negative); Strong pleochroism (dark brown to yellow-brown); non-fluorescent.
Hardness & Durability
Origin Region
Prominent sources include Brazil, Australia, Madagascar, and Sri Lanka. Often found in metamorphic rocks and pegmatites.
Hardness & Durability
Mohs Hardness: 7.0 - 7.5; Excellent durability for jewelry, though massive/heavily included specimens are more prone to fracturing.
Care & Maintenance
Avoid sudden temperature changes and ultrasonic cleaners if internal fractures are present. Clean with warm, soapy water and a soft brush.
Rarity & Value
Relatively common; value is determined by transparency and color purity. Dark/opaque massive specimens are low-cost, while gem-quality transparent golden-brown dravite is highly valued.
Special Characteristics
Strongly dichroic; displays piezoelectricity and pyroelectricity (generates electric charge under pressure or heat).
Lore & History
Historically used as a 'grounding stone.' Ancient lore suggests it promotes stamina and self-acceptance. Associated with the Root and Solar Plexus chakras in traditional crystal healing.