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, 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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