Knife River Flint is a high-quality, translucent, dark-brown chalcedony primarily sourced from the Knife River area in North Dakota. It is prized by collectors and lapidaries for its exceptional conchoidal fracturing properties, which historically made it a favored material for Native American stone tool production.
Is this knife river 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 knife river flint with a known reference. Knife River Flint sits at Mohs 6.5-7 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Knife River Flint leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Knife River Flint typically shows a waxy luster.
- 4Match the color rangeCompare against the expected color range: brown, dark brown, yellowish-brown.
- 5Look at form & habitCrystal system: trigonal. Typical habit: massive.
Often confused with
Knife River Flint vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside knife river flint
Minerals reported to co-occur with knife river 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
- 6.5-7
- Density
- 2.60-2.65 g/cm³
- Streak
- White
- Luster
- Waxy
- Transparency
- Translucent
- Crystal system
- Trigonal
- Crystal habit
- Massive
- Cleavage
- None
- Rarity
- Uncommon
- Uses
- Lapidary, Collector, Tools
- Host rock
- Sedimentary Deposits
- Typical price
- $10-100 per specimen
Where rockhounds find knife river flint
1 mapped spotsClassic worldwide localities
- North Dakota, USA
Field-hunting tip
Look in sedimentary deposits country — that is the host setting where knife river flint typically forms. If you start seeing quartz, chalcedony 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 North Dakota — start trip planning there.
Common questions
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Find knife river flint on the map
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