Coal is a combustible sedimentary rock formed from ancient plant matter that has been buried and subjected to heat and pressure over millions of years. It varies significantly in quality and carbon content, ranging from soft brown lignite to hard, shiny anthracite. Collectors typically look for specimens showing clear plant impressions or distinct layering.
Is this coal?
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 coal with a known reference. Coal sits at Mohs 0.5-2.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Coal leaves a black streak.
- 3Read the lusterHold the specimen under a strong light. Coal typically shows a dull to submetallic luster.
- 4Match the color rangeCompare against the expected color range: black, brown.
- 5Look at form & habitTypical habit: massive.
Often confused with
Coal vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside coal
Minerals reported to co-occur with coal. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Mohs hardness
- 0.5-2.5
- Density
- 1.1-1.5 g/cm³
- Streak
- Black
- Luster
- Dull to Submetallic
- Transparency
- Opaque
- Crystal habit
- Massive
- Cleavage
- None
- Rarity
- Common
- Uses
- Industrial, Fuel, Collector
- Host rock
- Sedimentary Coal Seams
- Typical price
- $2-20 for specimens
Where rockhounds find coal
1 mapped spotsClassic worldwide localities
- USA
- China
- Australia
- India
- Germany
Field-hunting tip
Look in sedimentary coal seams country — that is the host setting where coal typically forms. If you start seeing pyrite, siderite, kaolinite in float, you are in the right ground. Field specimens usually show a massive habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Montana — start trip planning there.
Common questions
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Find coal on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
