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 — that is 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.
Common questions
How do you identify black flint?+
Where is black flint found?+
Can I find black flint in the United States?+
How much is black flint worth?+
What rocks look like black flint?+
What minerals are found with black flint?+
What kind of rock does black flint form in?+
What is black flint used for?+
Find black flint on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
