Jet is a mineraloid formed from decayed wood under extreme pressure in sedimentary rocks. It is light in weight and warm to the touch, often displaying a high, glossy luster when polished, which made it a popular mourning jewelry material in the Victorian era.
Is this jet?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch jet with a known reference. Jet sits at Mohs 2.5-4, softer than the next harder reference, harder than the previous one.
- 2Name the organismDecide what left the fossil before worrying about the rock. Organism: Wood, commonly of trees in the family Araucariaceae. Age: Whitby jet: Early Jurassic (about 181 million years ago).
- 3Check the preservationPreservation: Decomposed, carbon-compressed wood. That controls the weight, the hardness and how the piece takes a polish.
- 4Read the lusterHold the specimen under a strong light. Luster: resinous.
- 5Match the color rangeCompare against the expected color range: black, dark brown.
Often confused with
Jet vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Obsidian is the harder of the two (Mohs 5-6 vs. 2.5-4); luster reads resinous on Jet and vitreous on Obsidian.
How to tell apart: Black Tourmaline is the harder of the two (Mohs 7-7.5 vs. 2.5-4); luster reads resinous on Jet and vitreous on Black Tourmaline.
Often found alongside jet
Minerals reported to co-occur with jet. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Mohs hardness
- 2.5-4
- Density
- 1.30-1.35 g/cm³
- Colors
- Luster
- Resinous
- Transparency
- Opaque
- Rarity
- Common
- Uses
- Lapidary, Jewelry, Collector
- Host rock
- sedimentary shale
- Organism
- Wood, commonly of trees in the family Araucariaceae
- Age
- Whitby jet: Early Jurassic (about 181 million years ago)
- Preservation
- Decomposed, carbon-compressed wood
Where rockhounds find jet
1 mapped spotsClassic worldwide localities
- Whitby, England
- Asturias, Spain
- Dorset, England
- Utah, USA
Field-hunting tip
Where it forms: sedimentary shale. If you start seeing pyrite, calcite, shale in float, you are in the right ground. In the U.S., the densest reported localities are in Utah. Start trip planning there.
Common questions
How do you identify jet?+
Where is jet found?+
Can I find jet in the United States?+
What rocks look like jet?+
What minerals are found with jet?+
What kind of rock does jet form in?+
What is jet used for?+
Find jet on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
