Black Tourmaline
Tourmaline supergroup, Schorl variety · Semi-Precious Gemstone and Mineral Specimen
Crystal System
Trigonal, typically forming prismatic crystals with striated faces, often occurring in massive, columnar, or tumbled forms.
Mineral Group
Silicates, specifically Cyclosilicates
Chemical Formula
NaFe3+2Al6(Si6O18)(BO3)3(OH)4
Formation Process
Primarily forms in igneous and metamorphic environments, specifically in granite pegmatites and hydrothermal veins through pneumatolytic processes at high temperatures and pressures.
About This Crystal
The specimen is a smoothly tumbled, polished black tourmaline (schorl). It has an opaque, solid black coloration with a high-gloss vitreous to sub-metallic luster on its polished surface, showing smooth curves and rounded edges characteristic of tumbled stones.
Physical Characteristics
Color is deep solid black. Streak is white. Cleavage is indistinct on prismatic faces, fracture is uneven to conchoidal. Specific gravity is approximately 3.0 to 3.2. Tenacity is brittle, though schorl is relatively durable.
Optical Properties
Uniaxial negative with strong birefringence and notable pleochroism in transparent varieties, though opaque schorl exhibits complete light absorption.
Hardness & Durability
Origin Region
Found globally with notable sources in Brazil, Pakistan, Afghanistan, USA (California, Maine), and Madagascar. Forms in pegmatites and hydrothermal veins.
Hardness & Durability
Mohs hardness rating of 7 to 7.5. Good durability making it suitable for most types of jewelry, though tumbled stones are primarily used as pocket stones or for wire-wrapping.
Care & Maintenance
Clean with warm soapy water and a soft cloth. Avoid harsh chemical cleaners and ultrasonic cleaners if internal fractures are present. Store separately from softer stones to prevent scratching.
Rarity & Value
Common and widely available. Value is very accessible, making tumbled specimens affordable for collectors and enthusiasts. Treatments are generally not performed on black tourmaline.
Special Characteristics
Exhibits strong pyroelectric and piezoelectric properties, generating an electrical charge when heated or subjected to mechanical pressure.
Lore & History
Historically used as a protective talisman against negative energies and psychic attack. In modern crystal healing, it is heavily associated with the Root Chakra for grounding, protection, and purification.