What is French jet?
By Jared James · Last updated 21 May 2026
Definition
French jet is black glass manufactured to simulate genuine jet, which is a form of fossilised coal mined mainly from Whitby in Yorkshire. It became popular during the Victorian mourning jewellery era when demand for jet outstripped supply, and glassmakers in France and elsewhere produced an affordable alternative in quantity. French jet has a glassier, more uniform surface than true jet, which is slightly lighter in weight and warmer to the touch. Both appear in antique brooches, necklaces and earrings from the 19th century.
Frequently asked questions
- How do you tell French jet from real jet?
- The easiest tests are weight and warmth: real jet is very light and warms quickly in your hand because it is organic material, while French jet is glass and feels heavier and cooler. Genuine jet also shows a brown streak if scratched on unglazed porcelain.
- Is French jet valuable?
- French jet pieces are generally less valuable than genuine Whitby jet, but fine Victorian examples with good craftsmanship still attract collectors. The value sits more in the age, condition and design of the piece than in the material itself.
- Is French jet the same as black glass?
- Yes, the terms are used interchangeably for the same material. It is black glass pressed or moulded into jewellery shapes, and French jet is simply the antique trade name that stuck.
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