Black flint is a hard, cryptocrystalline form of quartz typically found as nodules within chalk formations. It is well-known for its conchoidal fracture, which creates razor-sharp edges that have been utilized for tools and weapons for millennia.
Is this black flint?
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 black flint with a known reference. Black Flint sits at Mohs 7, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Black Flint leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Black Flint typically shows a waxy luster.
- 4Match the color rangeCompare against the expected color range: black, dark gray.
- 5Look at form & habitCrystal system: trigonal. Typical habit: nodular.
Often confused with
Black Flint vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside black flint
Minerals reported to co-occur with black flint. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- SiO₂
- Mohs hardness
- 7
- Density
- 2.6-2.66 g/cm³
- Streak
- White
- Luster
- Waxy
- Transparency
- Opaque
- Crystal system
- Trigonal
- Crystal habit
- Nodular
- Cleavage
- None
- Rarity
- Common
- Uses
- Lapidary, Collector, Historical Toolmaking
- Host rock
- Sedimentary Chalk Deposits
- Typical price
- $5-50 for hand-sized nodules
Where rockhounds find black flint
1 mapped spotsClassic worldwide localities
- United Kingdom
- France
- Denmark
- Belgium
- Germany
Field-hunting tip
Look in sedimentary chalk deposits country, the host setting where black flint typically forms. If you start seeing chalk, calcite, quartz in float, you are in the right ground. Field specimens usually show a nodular habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Ohio. Start trip planning there.
More black flint photos
Common questions
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Find black flint on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
