Jet
Lignite (Jet variety) · Organic Gemstone
Crystal System
Amorphous (Non-crystalline)
Mineral Group
Organic materials (fossilized wood)
Chemical Formula
C (with approximately 12% water and various mineral inclusions such as Pyrite or Quartz)
Formation Process
Sedimentary - Formed by the high-pressure decomposition of driftwood (mostly from the Araucariaceae family) in anaerobic seafloor conditions over millions of years.
About This Crystal
A dense black to dark brown organic material. It appears opaque with a dull surface when unpolished but displays a high vitreous to waxy luster when wet or polished. It has a smooth, velvet-like texture and is very lightweight compared to mineral stones.
Physical Characteristics
Color: Deep black to cocoa brown. Streak: Brown. Cleavage: None. Fracture: Conchoidal (shell-like). Specific Gravity: 1.30 to 1.34 (very light). Luster: Vitreous to waxy. Fluorescence: Usually none.
Optical Properties
Opaque; lacks refractive index in the standard mineral sense due to its amorphous nature; exhibits no pleochroism, birefringence, or fire.
Hardness & Durability
Origin Region
Notable sources include Whitby (England), Asturias (Spain), and the Aude region (France). Found in sedimentary clay and shale layers.
Hardness & Durability
Mohs Hardness: 2.5 to 4.0. Toughness: Fair to brittle. Stability: Susceptible to temperature sudden changes and prone to cracking or crazing over long periods if dehydrated.
Care & Maintenance
Clean with a soft, damp cloth. Avoid ultrasonic cleaners, steam, and harsh chemicals. Store separately from harder gemstones to prevent scratching. Avoid prolonged exposure to direct heat or intense sunlight.
Rarity & Value
Uncommon in high gemstone quality. Value is driven by size, lack of cracks, and historical provenance (Whitby Jet being most valuable). Often imitated by anthracite coal, glass, or plastic (epoxy).
Special Characteristics
Produces a static charge when rubbed (triboelectric effect). Often contains microscopic pyrite inclusions. It is warm to the touch compared to cold mineral gemstones.
Lore & History
Widely used for mourning jewelry during the Victorian era. Ancient Romans used it as protective amulets. Historically believed to ward off the 'Evil Eye' and used in traditional practices for grounding and protection.