Where is Jet found?
Lignite (a variety of coal)
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Open the appJet occurs in specific geological environments. Knowing where to look, and in what kind of rock, is the difference between going home empty-handed and finding a great specimen.
Where to find Jet
Whitby, North Yorkshire, England
World-renowned source of high-quality Jet, particularly from the Upper Lias (Jurassic) shales. This is the classic 'Whitby Jet'.
Asturias, Spain
Another historically significant source of high-quality Jet, often found in Carboniferous deposits.
France
Deposits found in various regions, including the Aude department.
Germany
Occurrences in several coal-bearing formations.
Turkey
Known for 'Oltu Stone', a type of jet.
United States
Found in various states, including Utah, Colorado, and New Mexico, often associated with Cretaceous coal beds.
Russia
Deposits in several coal-rich areas.
Collecting tips
- Look in Sedimentary Environments. Jet is found in sedimentary rocks, particularly shales and sandstones that were deposited in ancient marine or estuarine environments where wood could be buried and preserved.
- Associated with Coal Seams. While distinct from common coal, jet often occurs in proximity to or within coal-bearing strata, especially lignite or sub-bituminous coal deposits.
- Check for Lightweight Material. Jet is remarkably lightweight for its size. If you find a black, dense-looking material that feels unusually light, it could be jet.
- Observe Fracture and Luster. Look for a conchoidal (shell-like) fracture and, if broken, a dull to greasy luster on the fresh surface. Polished pieces will have a high vitreous luster.
- Perform a Scratch Test (Carefully). Jet is relatively soft (2.5-4 on Mohs scale). It can be scratched by a steel knife. However, this test can damage the specimen, so use with caution on a less visible area.
- Hot Needle Test (Destructive). A definitive but destructive test: a hot needle applied to an inconspicuous part of jet will produce a smell of burning coal/wood. This will not happen with glass or obsidian. Use with extreme caution and only if necessary for identification.
Quick Check
- Color:
- Deep black
- Luster:
- Vitreous (polished), dull to greasy (unpolished)
- Streak:
- Brownish-black
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