Author Topic: Finding "Flint"  (Read 10309 times)

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Half Axe

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Finding "Flint"
« on: April 17, 2013, 07:36:32 PM »
Now that two feet of snow in my area has brought just about everything to a grinding halt and I have finished shoveling snow, I've had some time to put this little essay together.  I hope some of you find it useful and informative.  I am a geologist by education and training and am licensed to practice geology in my state.

Finding "Flint" - a Geologist's Perspective
by
Half Axe

The following essay identifies some things to think about when searching for a suitable rock to act as a "flint" for striking sparks from a forged steel striker into a prepared tinder - a traditional method of fire starting used long before the advent of matches, butane lighters and ferrocerium rods. 

These qualities make a rock a good one for flint and steel fire starting applications: it must be harder than the steel striker, or it won't be able to strike sparks from it; it must be tough, so that it will hold up through repeated striking of the steel; it must break in such a way that a sharp edge is produced to strike against the steel; it must be commonly occurring, so that it can be easily replaced as it is used up.  Traditionally, the material which best exhibits all of these qualities is flint, a microcrystalline to cryptocrystalline, granular variety of solution-deposited quartz.

Hardness: the Mohs scale of hardness is a scale of relative mineral hardness developed by Austrian mineralogist Friedrich Mohs in 1824, who selected ten minerals for his scale.  The minerals, in order of increasing hardness, are: 1. Talc; 2. Gypsum; 3. Calcite; 4. Fluorite; 5. Apatite; 6. Orthoclase; 7. Quartz; 8. Topaz; 9. Corundum; 10. Diamond.  The Mohs test is a scratch test; if the test material will not scratch a mineral on the scale, it is softer than that mineral.  A good quality steel file, such as would be used to sharpen an axe, has a Mohs hardness of 6.5.  Such a file, even if worn down or broken, can be re-purposed to test rock specimens; if the file leaves a streak of metal on the rock, then the rock has potential for use as a "flint".

Tenacity:  in geologic terms, tenacity is defined as a mineral's resistance to breaking, crushing, bending or tearing.  As a general rule, rocks with a microcrystalline or cryptocrystalline texture have greater tenacity than other rocks.  Granite, for example, does not make a good "flint" because its macrocrystalline texture causes it to break along crystal boundaries and the individual crystals end up being crushed.  On the other end of the texture scale, obsidian has an amorphous texture which gives it a Mohs hardness of 5 and makes it too soft to be a good "flint".

Cleavage and Fracture: cleavage is the tendency of a mineral to break along its crystallographic planes (crystal faces), which reflects its crystal structure.  Crystal faces are external expressions of weaknesses in the crystal structure; the atomic bonds are weaker perpendicular to the crystal face and stronger parallel to the crystal face.  Rocks with well-defined cleavage do not make good "flints" because they break up rapidly with repeated striking of the steel.  Fracture is the way a mineral breaks when it does not yield along cleavage; the atomic bond strength is, for all intents and purposes, equally strong in all directions.  Of the four types of fracture, rocks which exhibit conchoidal fracture - a smooth, curved fracture which resembles the interior of a clam or oyster shell, commonly seen in glass or obsidian - have the best potential for use as a "flint".

Chalcedony, Chert and Flint:   Much confusion exists regarding these terms in common use.  In geologic terms, microcrystalline (crystals only recognized and distinguished under a standard microscope) and cryptocrystalline (crystals too small to be seen under a standard microscope, only distinguished using advanced methods) varieties of solution-deposited quartz divide into two categories: fibrous and granular.  Chalcedony is the general term used for the fibrous (long, needle-like crystals) category, characterized by a waxy, translucent to transparent appearance.  Common varieties of chalcedony are: carnelian (red); sard (brown); chrysoprase (apple-green); agate (alternating layers with different colors in concentric bands); petrified wood (wood has been replaced by agate); onyx (alternating layers in parallel planes); sardonyx (onyx with sard alternating with white or black layers); heliotrope or bloodstone (green with small red spots of jasper).  The granular category is characterized by interlocking compact crystals of quartz smaller than 30 microns (a micron, or micrometer, defined as 0.001 mm or 0.000039 inch) in diameter, and a dull, opaque to slightly translucent appearance.  The granular varieties are almost identical in texture and are differentiated only by color and depositional environment.  Traditionally, chert exhibits white to variously light colors and occurs in bedded deposits, and flint is dark to black in color and occurs in nodules in chalk and soft limestone deposits.  In geologic literature, however, the terms chert and flint are essentially synonymous and used interchangeably, chert being used to describe nodules and layered deposits in limestone and dolomite, and flint being referred to as a dark gray or black variety of chert.  To add to the confusion, jasper is alternately defined as chert associated with iron ores and containing iron oxides which imparts a red color, or any red chert or chalcedony regardless of association with iron ores.  Prase is a green variety similar to jasper, and occurs with it.  Either category will, as a general rule, serve very well as a "flint".

Definitions used in the paragraphs above are adapted from American Geological Institute publications and Hurlbut and Klein's Manual of Minerology.
« Last Edit: April 17, 2013, 07:52:54 PM by Half Axe »

Offline wolfy

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Re: Finding "Flint"
« Reply #1 on: April 17, 2013, 07:45:00 PM »
Thanks Half Axe.....good post!   I actually remember some of that stuff from a geology course I took in college, but I'm glad I don't have to worry about taking a quiz on it tomorrow! :P
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Half Axe

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Re: Finding "Flint"
« Reply #2 on: April 17, 2013, 07:58:47 PM »
You're welcome, Wolfy.  If you ever have to take that quiz, I'm happy to help you out.  I know rocks like I know the top of my...............sh oes.  ;)


Offline PetrifiedWood

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Re: Finding "Flint"
« Reply #3 on: April 17, 2013, 08:42:33 PM »
Great post Half Axe! Thank you!

This has potential to grow as folks add tips for "where" to find these rocks. I'm making it a sticky.

The best hint I can give on finding rocks that can be used for striking sparks is to actually carry a steel striker with you to test the rocks (similar to the file streak test mentioned above).

After experimenting a bit carrying your striker around and testing it on various rocks, you can get a feel for what will work.


Half Axe

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Re: Finding "Flint"
« Reply #4 on: April 17, 2013, 09:40:21 PM »
Thanks for making it a sticky, PW.  I wanted to post this up as my way to promote the flint and steel approach to starting a fire.  I know of many places in Wyoming where rocks suited to the method may be gathered at no or very minimal cost.

I'll start out on the "where to find it" part with two suggestions.  The first is to look along the base of limestone formations, especially where the limestone forms cliffs.  Chalcedony and chert deposited in solution cavities in the limestone will accumulate along the base as the limestone erodes over time.  The other suggestion is for city-bound folks who have a harder time escaping to the wilderness and may of economic necessity practice their bushcraft skills in their own back yard.  Many shopping centers and larger businesses use decorative rock or coarse gravel as part of their parking lot design.  Taking a little time looking them over will usually yield a few suitable rocks.  During the short time I lived in Minnesota, I gathered a handful of golf ball sized Lake Superior Agates while doing geotech work for parking lot resurfacing, just by looking through those decorative gravels during down time.

Offline PetrifiedWood

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Re: Finding "Flint"
« Reply #5 on: April 17, 2013, 09:53:32 PM »
In my immediate area it's all slate, shale and sandstone, but an hour's drive gets you to some places where smooth rounded stones that were once tumbled in water literally coat the ground, having been exposed by the soil eroding away. Most of them work for sparks once you bust them open to get at an edge. But they are mostly fist sized and smaller, and while they work for sparks they don't seem to have conchoidal fracture so they aren't useful for knapping material.

Half Axe

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Re: Finding "Flint"
« Reply #6 on: April 17, 2013, 10:15:36 PM »
PW, I'm going to have to lay my hands on a geologic map of Utah and see if I can't find you a better collecting area.  One of my consultants may be able to loan me a map.  I'll work on that as part of the "where to go" suggestions.

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Re: Finding "Flint"
« Reply #7 on: April 17, 2013, 10:19:57 PM »
I'm going to have to post a pic of some rocks I collected at a specific area and if I can find the coordinates I'll post those as well. I've been calling them chalcedony but I might be misidentifying them.

Might be a good thing to post that kind of info in the Utah local board. ;)




Offline PetrifiedWood

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Re: Finding "Flint"
« Reply #8 on: April 17, 2013, 10:29:18 PM »
These work very well for striking sparks, but do not flake easily, however I have found a piece at the deposit that appears to have been pressure flaked. As you can see, these were broken up long ago, they have some lichen growing on them in places.

This deposit was about a 2 hour drive from me. It was a slight depression in the land where they were strewn about everywhere in an area about the size of 2 football fields. A professor at the local college who also works at the prehistoric museum in the paleontology dept. (and from who I took a gem cutting class a few years ago) directed me there. I think I asked him where I could find "chert" at the time.




Half Axe

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Re: Finding "Flint"
« Reply #9 on: April 18, 2013, 06:01:03 PM »
They look like chalcedony from this angle, PW.  I'm sure they are.

In these photos, the red rock is jasper from the northwest end of Glendo Reservoir and the other is a piece of chalcedony I collected locally.  Note how the jasper has a dull appearance and the chalcedony is waxy-looking.





I wanted to use better examples in the photos, but my rock specimens are buried under a couple of feet of snow.  >:(

I'm going to post something of interest in the Utah board in a little bit for you to check out.

Offline PetrifiedWood

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Re: Finding "Flint"
« Reply #10 on: April 18, 2013, 06:09:30 PM »
Thanks! yep "waxy" would be a good description for this stuff. I might have a polished piece from the same deposit, if I can find it I will get a picture.

Offline PetrifiedWood

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Re: Finding "Flint"
« Reply #11 on: April 18, 2013, 06:17:25 PM »
Ok, I'm pretty sure this was collected at the same location, though I didn't collect it myself. I did polish it though.


Half Axe

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Re: Finding "Flint"
« Reply #12 on: April 18, 2013, 06:33:14 PM »
Definitely chalcedony, looks textbook.  Nice polish - it shined up like a new penny!

Offline MnSportsman

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Re: Finding "Flint"
« Reply #13 on: April 18, 2013, 07:19:21 PM »
Thanks Much Half Axe!
 :thumbsup:


I agree with PW on the having a striker with ya, but trying to scratch glass like a beer bottle or the like has worked for me also, when showing others how to test without them having a striker on hand. (For me... I carry one 99% of the time when I am out ;) , and sometimes a beer too...LOL )


  I live in S.E. Minn. {(North/upper side of the Glacial free zone) about 30 miles south of the TC.} and I find what I call "chert" all the time. What I find is mostly gray both dark & light. Don't think there is any "flint" type chert anywhere near here. But the stuff we have here is mighty good at sparking.
 :)


Thanks again for sharing your knowledge & insights!
 :D
I love being out in the woods!   I like this quote from Mors Kochanski - "The more you know, the less you carry". I believe in the same creed, & think  "Knowledge & honed skills" are the best things to carry with ya when you're out in the wilds. They're the ultimate "ultralight" gear! ;)

Half Axe

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Re: Finding "Flint"
« Reply #14 on: April 18, 2013, 08:37:03 PM »
Glad to share and promote the technology, MnS.  If you have any tips on where to go and what to look for in your area to collect the chert you speak of, I hope you'll post them here.

Offline MnSportsman

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Re: Finding "Flint"
« Reply #15 on: April 18, 2013, 09:04:46 PM »
:)


   I do have one suggestion for folks. Although it is likely a regional thing for this area, it may be the same in many other locales...When you are around commercial buildings like hospitals, schools, etc., and they have used rock for landscaping, you might be surprised at the finds you can see. I have found a lot of what I call "sparking rocks", (< since I am no geologist. ;) ) in urban/suburban locations like that, simply by looking at the rocks, when I am waiting for someone to come out of the building, or just having a smoke outside. Over the years I have developed an "eye" for the good ones. All it takes is a simple strike or a few to find out if it is a good one once you spot one. Not unlike finding a rock out in the sticks & trying it. Bridge rip rap is another place to search around for them.


    I also check waterways & lakes that have rocky shorelines. Along cliffs & the fallen rocks, etc..
 
     Those are not the only places I look, but it is a start for folks who want to start looking if they are around my area of Minnesota, & might work just as well in other areas of the world.


     I don't know if that helps anyone , Half Axe, but it was a try. If I think of anything else that could help I will return & say something here.
:)
I love being out in the woods!   I like this quote from Mors Kochanski - "The more you know, the less you carry". I believe in the same creed, & think  "Knowledge & honed skills" are the best things to carry with ya when you're out in the wilds. They're the ultimate "ultralight" gear! ;)

Half Axe

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Re: Finding "Flint"
« Reply #16 on: April 18, 2013, 09:30:55 PM »
Thanks!  :)

Offline Bearhunter

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Finding "Flint"
« Reply #17 on: April 18, 2013, 10:36:44 PM »
Ok, I'm pretty sure this was collected at the same location, though I didn't collect it myself. I did polish it though.



Wow, that's beautiful 8)

Nice post Half Axe, thanks :thumbsup:
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Half Axe

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Re: Finding "Flint"
« Reply #18 on: April 19, 2013, 08:34:33 PM »
Here are some pictures of flint that exhibits conchoidal fracture.  The flint, from Platte County Wyoming, is white, but has a rind of weathered material colored by iron oxides.










Offline PetrifiedWood

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Re: Finding "Flint"
« Reply #19 on: April 19, 2013, 10:47:31 PM »
Now that looks like a good piece for striking!

Offline wgiles

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Re: Finding "Flint"
« Reply #20 on: April 20, 2013, 05:36:48 AM »
I have a few flint nodules that came from the Red River Gorge area in Kentucky. While it is possible to find them on your own, I bought these from a roadside vendor. They are supposed to be of high quality, suitable for knapping. I haven't tried to do anything with them, but they look like they should make some nice flakes. They are dark and would appear to have quite a bit of iron oxide in them. I have found chert in Missouri, but it is generally off white to tan. The chert makes sharp flakes, but appears to be harder to work. Since my ability to work flint or chert is practically non existant, I wouldn't depend on my descriptions. We do find arrowheads in central Illinois, but the only flint or chert would have been brought down by the glaciers. We find granite and other rocks and boulders in the glacial till that originated far away.

Half Axe

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Re: Finding "Flint"
« Reply #21 on: April 20, 2013, 08:50:46 PM »
Now that looks like a good piece for striking!

It works very well!  :)

I need to get out and find more like it this summer.

Half Axe

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Re: Finding "Flint"
« Reply #22 on: April 20, 2013, 08:59:54 PM »
I have a few flint nodules that came from the Red River Gorge area in Kentucky. While it is possible to find them on your own, I bought these from a roadside vendor. They are supposed to be of high quality, suitable for knapping. I haven't tried to do anything with them, but they look like they should make some nice flakes. They are dark and would appear to have quite a bit of iron oxide in them. I have found chert in Missouri, but it is generally off white to tan. The chert makes sharp flakes, but appears to be harder to work. Since my ability to work flint or chert is practically non existant, I wouldn't depend on my descriptions. We do find arrowheads in central Illinois, but the only flint or chert would have been brought down by the glaciers. We find granite and other rocks and boulders in the glacial till that originated far away.

How big are those nodules?  We used to have some flint knappers around here, maybe they could give you some advice (my skills in flint knapping are pretty basic).  Good luck with it!

Offline Gurthy

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Re: Finding "Flint"
« Reply #23 on: April 28, 2013, 04:53:04 PM »
How did I miss this post until now!?!?! Great bunch of info here!

I've done a little research for "flint" in my area and it seems that the Natives mined it from the Saginaw Bay area (near the city of Flint, MI not unsurprisingly). It is referred to as Bayport chert. Here is a link to some info with pics of some artifacts: http://www.arrowheads.com/paleo/424-michigan-paleo-and-bayport-chert

More locally I have a few open quarries and creek/river beds and banks that I have scouted for "flint" rocks without much success. I was, however, looking for rocks that were well-suited to knapping, and my method of testing consisted of smashing little rocks with big rocks to see if they would fracture in a manner that would suggest usefulness. Not very scientific, I know :)  Now that I'm armed with more info I'll return to those areas and see if I can find some good rocks for use with steel strikers.

Half Axe

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Re: Finding "Flint"
« Reply #24 on: April 29, 2013, 05:47:35 PM »
Gurthy, here is a link to a maps page that might help you out:

http://mgs.geology.wmich.edu/MGS/MGS_maps.shtml

Select the bedrock geology map, it will give you an idea of where the Bayport Limestone is potentially exposed at the ground surface.  I say potentially, because much of the bedrock in LP Michigan is buried under glacial deposits (and vegetation).  If you look where drainages cut across the formation, you will stand a better chance of finding the limestone exposed.  The chert will most likely be found as nodules in the limestone.  Those nodules will weather out and accumulate at the base of the limestone.  Happy hunting - let us know how you do!

Offline Gurthy

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Re: Finding "Flint"
« Reply #25 on: April 29, 2013, 09:11:49 PM »
Thanks Half Axe... there are some great resources in that link!

Offline Little Yellow Jacket

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Re: Finding "Flint"
« Reply #26 on: July 17, 2013, 02:24:08 PM »
Thanks for the education. I picked up a small slab of what I thought was "flint" in the desert in west Texas a month or so back. It's about the size of your hand and maybe 2" thick. Now I know how to see how hard it is where a half hour ago I didn't know I needed to.
Rick

Half Axe

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Re: Finding "Flint"
« Reply #27 on: July 19, 2013, 06:36:52 AM »
You're welcome, LYJ.  Post any questions you may have.

Offline FlaMike

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Re: Finding "Flint"
« Reply #28 on: July 19, 2013, 07:08:28 AM »
I did do some knapping a few years ago, collected a pretty good selection of "abo" tools, as opposed to the more "modern" copper ones. Nothing against the modern version of knapping, its just that the paleolithic version interested me more.

Living in Florida, the local material would have been a chert and for me, I guess it would be what is called Hernando Chert. The other material would be fossilized corals. Looking at some of the rockhound sites, I've seen some beautiful fossilized corals. Most seems to have been gathered at commercial rock quarries, where clubs are allowed in for a fee, to collect whatever they can find. I am NOT likely to join one of the clubs, so I'll have to see what I can find on my own.

From what I've been able  to learn, the local chert is hard to work, but is greatly improved by heat treating. And I've  heard the same for the corals. Not being interested enough to buy a proper kiln (have considered making one though,) I've read where there is evidence that the original inhabitants of the state would bury a spread of pre-forms under a layer of sand, sometimes several layers of the rocks separated by layers of sand, and then built fires on top, kept burning for the better part of a day. They would then let them cool naturally, and dig them up the next day.

Not exactly precise temperature control, but it seems  to have worked. This is something I'd like to try, should I locate some suitable rock and or coral.

Anyone heard of heat treating this way?

Mike S.
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Half Axe

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Re: Finding "Flint"
« Reply #29 on: July 21, 2013, 06:41:27 PM »
FlaMike, check out this thread:

http://bladesandbushcraft.com/index.php/topic,6183.0.html

I'd follow up with Crashdive123 on the particulars.

Offline FlaMike

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Re: Finding "Flint"
« Reply #30 on: July 22, 2013, 06:29:34 AM »
Thanks! I'll take a look.

Mike S.
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Re: Finding "Flint"
« Reply #31 on: January 30, 2014, 09:20:32 PM »
I find flint all the time and have bags full of it, I find it all in freshly plowed farm fields. Not only that but Ohio is blessed with flint. One place is called flint ridge and was a favorite place for Indians to gather and collect flint. If your state had Indians then you more then likely have flint in your area. Look for construction sites or stop and ask a farmer if you can walk his fields.

Half Axe

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Re: Finding "Flint"
« Reply #32 on: January 31, 2014, 07:32:43 PM »
Thanks for posting, offtrail - great suggestions on places to look.

Offline skagun

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Re: Finding "Flint"
« Reply #33 on: February 13, 2014, 07:14:51 PM »
I have limestone cliffs here in the county that I just know has flint in it, but I'll be dogged if I can find any!  there is an actual chirt pit east of me but I try to avoid that if I can help i.  I'd prefer a good "true" flint if I can find it and save the chirt as a last resort.  the nodules I have just don't seem to fracture  well.  I'm aware that part of my problem is that I need to be master than the rock. :P

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Re: Finding "Flint"
« Reply #34 on: February 19, 2015, 06:02:31 PM »
Texas seems to be blessed with an abundance of chert/flint.  I have found plenty of good sparking rock in landscaping rocks.  Nice round nodules about the size of an orange and covered with a brown layer of something. When you find one that is black on the inside, it works well.
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Offline NewEnglandBushcraft

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Re: Finding "Flint"
« Reply #35 on: September 06, 2015, 02:52:43 PM »
Aside from colonial sites, especially battle sites, the northeast is pretty much devoid of chert. But what we do have is an abundance of quartz, and in sandy soils, lots of quartzite. Both make excellent stone tools, and I work with both. Quartzite, however, can be extremely difficult to fracture because its just so tough...you may find that grinding would be the better option than knapping. Quartz can be an odd material to work. Quartz found on the surface is often weakened with frost cracks that will effect flaking and spalling...not necessarily bad, but it will dictate what you can and cannot make from the piece. That said, quartz is much easier to fracture than quartzite, though the edges can crumble/be crushed during flake removals depending on the quality of the material. Don't expect large blade flakes to pop off during spalling with quartz and quartzite. The Native stone tool artifacts tend to be clunky compared to other parts of the country where cherts, jasper, agates, and obsidian can be found.

Good quality quartz and quartzite can be found on river and stream beds or wherever water has flowed. Gravel/sandy beds that carry runoff can be good places to look as well. Trails with loose rocks are also worth checking. The best stones are mined where the elements have not altered them.
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Re: Finding "Flint"
« Reply #36 on: September 06, 2015, 04:07:19 PM »
Good tips, NEB.......I learned something new. :P :thumbsup:
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Offline duxdawg

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Re: Finding "Flint"
« Reply #37 on: November 11, 2015, 06:12:08 PM »
Great post Half Axe! More detail than most include. 

I have gathered "flint" from half the States in the CONUS. Quartzes, dolomite, granites, sandstones, cherts, agates, onyxes, etc. Not being a rockhound I have not formally identified most of them.

Carbide steel works as the "flint" if you're short on suitable rocks.

In addition to scratching glass, looking at the fractures, chalky cortex, glassy, waxy, shiny, sparkly, etc characteristics for identifying suitable rocks to use as the "flint" in F&S, there is another way. Triboluminescence.

Triboluminescence is the sparks generated when you have one quartz containing rock and strike or scrape another quartz containing rock against it. Best seen in a darkened area. These weak, tiny electric sparks are mostly within the rocks. They can be blue, white, yellow, orange or red, No, they will not ignite any char.

So if you have a rock you know has any form of quartz (chalcedony, chert, flint, etc) in it and when you strike or scrape an unknown rock against it you get sparks, then you now know the unknown rock also contains quartz. If it contains quartz, it will almost certainly work as "flint" as long as you can get a sharp edge on it.

Offline caoutdoorsman

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Re: Finding "Flint"
« Reply #38 on: November 24, 2015, 10:58:52 PM »
Very helpful, thanks for posting! 8)