Jet

Jet fossilised wood including Whitby jet, properties, Victorian significance, identification, and distinguishing from simulants.

species/jet whitby mourning-jewellery victorian organic

Introduction

Jet is fossilised wood (a form of lignite coal) that has been used as a gem
material since prehistoric times. Most famous from Whitby, England, jet was
extremely popular in Victorian mourning jewellery after Prince Albert's death.

Unlike coal, which crumbles, jet is compact and takes an excellent polish,
making it suitable for carving and jewellery.

Formation and Composition

How jet forms:

Formation Process

  1. Wood (often Araucaria trees) falls into water
  2. Becomes waterlogged and sinks into sediment
  3. Anaerobic conditions prevent complete decay
  4. Heat and pressure over millions of years
  5. Carbon-rich compact material forms

Composition

  • Origin: Fossilised driftwood
  • Type: Compact lignite coal
  • Age: Jurassic period (~180 million years for Whitby)
  • Carbon content: High (similar to coal)

Physical Properties

Property Value
Hardness 2.5-4 Mohs
Specific gravity 1.30-1.35 (very light)
Refractive index 1.66 (spot; often difficult)
Lustre Waxy to vitreous when polished
Colour Black (brown in thin sections)
Fracture Conchoidal

Types of Jet

Jet quality varies by source:

Hard Jet

  • Forms in saltwater (marine) conditions
  • More compact and durable
  • Takes better polish
  • Higher value
  • Whitby jet is this type

Soft Jet

  • Forms in freshwater conditions
  • Less durable
  • May crack over time
  • Lower value
  • More common

Whitby Jet

Victorian Mourning Jewellery

Jet's historical significance:

The Victorian Era

  • Prince Albert died in 1861
  • Queen Victoria wore jet mourning jewellery
  • Fashion followed the Queen's example
  • Whitby jet industry boomed 1860s-1880s
  • Over 1,400 jet workers in Whitby at peak

Mourning Jewellery Types

  • Brooches and pendants
  • Necklaces and bracelets
  • Carved cameos and intaglios
  • Crosses and religious items
  • Hair jewellery with jet components

Identification

Distinguishing jet from simulants:

Material SG Feel Test
Jet 1.30-1.35 Warm; light Coal smell when heated
Black glass (French jet) 2.3-2.5 Cold; heavy No smell; may show bubbles
Vulcanite (hard rubber) 1.1-1.2 Rubbery; very light Rubbery/sulphur smell
Bakelite 1.25-1.35 Plastic feel Carbolic acid smell
Black onyx 2.65 Cold; heavy Much harder (H 7)
Bog oak ~1.2 Woody grain Wood smell; shows grain

Hot Needle Test

Care and Durability

Jet care considerations:

Advantages

  • Warmer to touch than glass simulants
  • Lightweight for large pieces
  • Takes excellent polish
  • Relatively durable for organic gem

Care Guidelines

  • Store separately from harder gems
  • Clean with damp cloth
  • Avoid harsh chemicals
  • Polish gently if needed
  • Avoid extreme heat or dryness
  • Can crack if dried out (especially soft jet)

Market Considerations

Jet market factors:

  • Antique value: Victorian pieces collectible
  • Whitby premium: Genuine Whitby commands higher prices
  • Modern production: Limited Whitby; Spanish jet available
  • Simulants common: Much "jet" is glass or plastic
  • Provenance important: Documentation adds value

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