Black Spinel
Spinel (variety Pleonaste or Hercynite) · Semi-Precious Gemstone / Collector Gem
Crystal System
Cubic (Isometric); typically occurs as octahedral crystals or massive granular forms.
Mineral Group
Oxides / Spinel Group
Chemical Formula
MgAl2O4 (often with Fe2+ substituting for Mg in black varieties)
Formation Process
Metamorphic, primarily through contact metamorphism of limestones and dolostones. Also found in igneous rocks such as basalt.
About This Crystal
Deep jet-black stones with a bright, vitreous (glass-like) luster. These gems are opaque, lacking transparency, and when faceted, provide a mirror-like finish superior to black tourmaline or onyx.
Physical Characteristics
Color: Opaque black. Streak: White. Cleavage: Indistinct/None. Fracture: Conchoidal. Specific Gravity: 3.54 - 3.63. Tenacity: Brittle. Generally non-fluorescent.
Optical Properties
Singly refractive; Refractive Index: 1.710 - 1.735. No birefringence or pleochroism due to cubic structure.
Hardness & Durability
Origin Region
Thailand, Myanmar (Burma), Sri Lanka, and Vietnam; found in contact metamorphic limestones and alluvial deposits.
Hardness & Durability
Mohs Hardness: 8.0. Excellent durability and toughness, making it highly suitable for daily jewelry wear compared to softer black stones like jet or onyx.
Care & Maintenance
Clean with warm, soapy water and a soft brush. Ultrasonic and steam cleaning are generally safe unless the stone has significant fractures. Store separately to avoid scratching softer gems.
Rarity & Value
Relatively common but highly valued as a high-quality alternative to black diamond. Value is determined by the quality of the cut and polish; typically affordable ($10-$50 per carat). Natural and usually untreated.
Special Characteristics
Known for its exceptionally high luster and 'adamantine-like' sparkle when faceted in small rounds (pavé setting as seen in the image).
Lore & History
Historically often confused with black diamond or magnetite. In traditional lore, it is considered a stone of protection and grounding, believed to repel negativity and provide stamina to the wearer.