Schorl (Black Tourmaline) with possible Pyrite
Tourmaline var. Schorl with minor sulfides · Semi-Precious Gemstone / Mineral Specimen
Crystal System
Trigonal; typically prismatic crystals with vertical striations, often forming dense, columnar or massive habits.
Mineral Group
Silicates (Cyclosilicates); Tourmaline group.
Chemical Formula
NaFe2+3Al6(Si6O18)(BO3)3(OH)3(OH)
Formation Process
Igneous and Metamorphic; primarily formed in pegmatite veins and metamorphic schists through hydrothermal activity.
About This Crystal
Opaque, jet-black to brownish-black specimen with an irregular, fractured habit; exhibits a vitreous to sub-metallic luster on fresh surfaces and characteristic longitudinal striations.
Physical Characteristics
Color is black; streak is white to gray; no distinct cleavage; conchoidal to uneven fracture; specific gravity of 3.0-3.25; strongly brittle; typically non-fluorescent.
Optical Properties
Opaque; uniaxial negative; high refractive index (~1.61 to 1.66); no pleochroism visible due to opacity, though thin edges may show brown.
Hardness & Durability
Origin Region
Notably from Brazil, Namibia, Pakistan, and the USA (California and Maine); found in granitic pegmatites.
Hardness & Durability
Mohs Hardness: 7 to 7.5; high durability and resistance to chemicals but prone to splitting along fractures.
Care & Maintenance
Clean with warm soapy water and a soft brush; avoid ultrasonic or steam cleaners as they may aggravate internal fractures.
Rarity & Value
Abundant and common; value is generally low unless in large, perfect aesthetic crystal clusters; typically untreated.
Special Characteristics
Strongly pyroelectric and piezoelectric (generates an electrical charge when heated or compressed).
Lore & History
Historically used as a 'mourning stone' in Victorian jewelry; traditionally believed to be a stone of protection and grounding to repel negative energy.