Testing rock for flint

[evfreek]

Hi.  I visited an Indian trading post near Four Corners, NM, and one of the sellers told me that the rocks that they sell with drawings on them are flint, and will throw sparks when struck with a fire steel.  They did not have any blank rocks, but they said that the flint was very hard to find in the outcrops, most of the rock being sandstone.  I found some rocks which looked promising, but they did not create sparks when struck with a file tip.  Is this a valid test?  Does this kind of flint throw sparks?  Is there a good test or way of recognizing flint that is usable with a fire steel?  I'm just curious.  The only thing I have gotten sparks from is mischmetal.

 

 

[ThomasPowers]

As a degreed geologist I can't tell what kind of rock you are describing.

 

Flint doesn't throw the spark flint carves off a micro chip of steel that burns and that is the spark.

 

Yes you can learn to recognize likely rocks; looking at ones known to be good helps to train the eye.

 

Pretty much all flint will throw a spark until you get down to the fairly earthy cherts.

 

How do you know if "this kind of flint" *is* flint if you don't know what flint is?

[ianinsa]

I clicked on this thread cause the only flint I know is the round 'jobbie ' that looks like a piece of pencil lead that you find in a 'bic' lighter and the ones on O/A strikers.

I certainly don't know what it looks like 'in the rough'.

I said to myself " you could learn something here", well silly old me!

[Frosty]

Okay, field testing stone for striking sparks. It doesn't NEED to be flint, just hard and durable enough to shave a bit of hard steel when struck. Your best bet will have a fine grain, maybe look like fired clay. When fractured it will cleave with a concoidal fracture. Use a sharp edge of the fracture and strike it along the flint in a grazing blow. If it sparks you're good to go.

 

That's it, it has to be hard and strong, obsidian is WAY sharper but it way too fragile. Flint through friable chert work fine on strikers as will quartz, granite, gneiss, etc. Make a fresh fracture and strike it along the steel.

 

This is an example of why I usually don't call them "flint" strikers, I'm probably not using flint. One of my peeves (not listed in the other thread) is sloppy language, especially be nominally "educational" sources. It just KILLS me to listen to the narrator, archeologists, etc. referring to "flint" knapping obsidian, over and over through a program. Lots of stones will strike a spark, just rake a ball pein across pavement or drag a chain behind the pickup.

 

Frosty The Lucky.

[BIGGUNDOCTOR]

Got any friends in Texas? There is flint outside of Fort Hood, that is where my Dad got a big hunk of it. White on the outer crust, gray on the inside.

That is an issue with rocks, often they look totally different on the outside surfaces than what you normally see. Take a hammer with you on your rock hounding trips. May also want to contact a local gem and mineral society.

[1forgeur]

To test a rock on a file, you have to use the edge of the file. There cannot be any teeth on the edge, it has to be smooth or it will not spark. You would have to grind the teeth off the edge of the file to use it. And like Thomas says, the rock has to be hard enough and sharp enough to carve a chip off the file or striker. This has been my experience with using files as strikers.

[ThomasPowers]

ianinsa; you expected to learn about geology on a blacksmithing site?  As you suspected the "flints" in lighters are not made from flint; they are made from ferrocerium a man made material.

 

Frosty; you should see the geological hackles rise anytime an archeologist calls any green rock "jade".  At least they are getting better about "copper alloy" instead of "bronze"

 

Shall we muddy the water further and mention the use of iron pyrites in wheellocks locks?

 

A bit more to the point may I commend to your attention searching on Google with:       finding flint in california 

For a large number of quite helpful sites on the very first page!  Including:

How to find flint suitable for flint and steel in Fire Making Where can I find Flint/Chert in California? The Quartz Page: Flint and Chert Finding Flint / Chert Easily Part 2 - YouTube

 

and as mentioned many varieties of quartz will actually work, including flint, chert, jasper, etc,(look at the microcrystalline varieties first though I had excellent luck using quartz geodes from Brown County Indiana and a file for flint and steel)

[Charles R. Stevens]

Always fun to see some one ask a question (or have an arm chair expert open their "mouths") only to find out that one (or more) of the members realy is an expert.
No dumb questions, but if you ask one one you had really better want an answer! (And dont start the question in the middle if you don't want to incire Master Tommases Ire)

[ianinsa]

Thomas, :) you might be amazed at what I have learnt on this site(come to think of it YOU probably will not) the most unlikely thing was how grass brooms were made!

It is awesome at just how deep this well of knowledge is, along of course with some flotsam and jetsam. I'm saddened this we missed meeting up in the UK.

[1forgeur]

Come to central Illinois, you can find all the chert you you can carry in some fields. Most all of it I've found will make a spark. I'm not an expert on arrow heads, but I've found a few made of chert (I think) from the tractor when I was a kid. No tractor cabs back then, so we watched for arrow heads for something to do. They really showed up good in the spring after it rained. If the Indians could knap it, it will spark. My 2 cents worth on it.

[ThomasPowers]

Well obsidian is sort of the exception to the knappable/sparkable rule but it's a good rule anyway.

Flint Ridge in Ohio is a great place, the indigenous peoples traded the brightly covered flint for hundreds of miles and it was "accorded neutral territory" with the various tribes.

The Alibates flint of Texas is also well known

remember for many of these sites NO COLLECTING ON PARK LANDS! But there is usually plenty of place outside the boundaries to collect.

And England is world famous for their flint nodes in the chalk beds---exporting gun flints was a business at one time.

Ianinsa: does the Matjiesfontein White Band Marker chert make good sparks for flint and steel?

Now for local information: many community colleges have intro to geology courses and someone who should know local possibilities... If you are near a full University there will definitely be someone you can track down and talk too---remember that most folks in such departments are quite happy to try to lure folks into taking their courses by helping, (I remember running into a metallurgical conundrum and hunting down a Professor in a local State University's MatSci department who was happy to discuss things with us and his final statement was "Why aren't you in my classes!" as our speculation on what had occurred---heavy work hardening followed by fairly "low" temp heating resulting in areas of re-nucleation and areas of just grain growth--was spot on.)

[Charles R. Stevens]

State and federal experts are usualy helpful, tho my experiance isn't with geoligests (they may be haried and overworked?) but most of the time they are so exited that some one is interested in asking their advice that you will get much more than you asked for.

[Frosty]

I'm no expert, Dad was the rock hound, co founder of the Boeing Rock club, whatever it's called nowadays in fact. Then I spent almost 20 years as an exploration driller for bridges and foundations with the geology section of the Headquarters Materials Department of the State of Alaska department DOT. I was one of the guys with dirty hands and muddy clothes who lived in a tent most of the time. Made me a guy who was closely associated with guys holding multiple degrees and almost no hands on experience. Too many long stories there.

 

Dad was the expert mineralogist, was getting calls till his mind wasn't working well enough, into his late 80's. He didn't have a high school diploma, got his GED in the late 1980's to keep a job. He could do Calc and Trig in his head but it wasn't documented so it didn't count in the  management books. Isn't that part of the foundation of my gut level knee jerk low opinion of the entire "theory of management."

 

Back to the practical side of this thread, it's much harder for me to dig into the long ago parts of my memory without turning into a crusty old coot reminiscing about the "good old days."

 

If you're rockhounding for sparky rocks, why are you carrying a . . . file? You need a rock hammer,that would be a "geologist's pick" if you go to the store for one. Go to the hardware store and just buy one, will ya. It's a tool designed with thousands of years of experience behind it, more time and experience than blacksmithing in fact. It will look just like these. http://geology.com/store/rock-hammers/ In truth any old hammer will work but pick one like a driller's hammer or single jack sledge with a long back and short handle.

 

When you find a candidate just give it a stroke on the hammer. Use the back of the hammer like a striker!? :o You can do that?! Golly gosh it night strike a spark cracking a rock even! Ooooh! :blink:

 

Unless you need to pack a machete, leave the files home. Do take a ruck, lunch and plenty of water, your notebook & GPS (Dad would've KILLED for a GPS) should share a shirt or a cargo pocket with the colored pens and pencils. The "Roadside Geology of (whatever state you live in)" and "Atlas & Gazetteer" (your State's name here) is probably better kept in your car/truck/wheeler, etc. when you're hounding but sometimes should be in the ruck.

 

Now just read the Roadside Geology, take your best guess, plot a search pattern in the Gazateer, pack your camp gear choose a weekend for fun and exploration and GET OUT THERE!

 

Oh I suppose a person could contact the local Gem and Mineral Society and ask but that'd be the easy way and if we wanted to do things the easy way we wouldn't be blacksmiths now would we? Seriously if you want to light a fire the easy way you'd just buy a . . . Zippo or Bic. :huh:

 

Gotta go. Oh don't waste a whole lot of time trying to get a spark off Agate it's not a great candidate for sparks but if you want to knap a point or blade it's pretty decent for that and the results are flashy.

 

Frosty the Flaky.

[HWooldridge]

Most everything we dig out of the ground around here is either flint or limestone (or oil <_<) - some areas have more of those materials laying on the surface than usable soil for agriculture.  Must have been decent material for the ancient Amerindians as the stuff is everywhere.  Walk over any plowed pasture after a rain and you are liable to find some type of flint tool or point.

 

Re the OP question; some flints are much better at throwing sparks than others.  I have found some pieces that almost look like a grinding wheel spark spray when you hit them on a steel - others might throw one or two sparks over several strikes.

[ianinsa]

Wow, this has become an entertaining and informative thread, I'm glad I hung in there.

Matjiesfontein  only a 9 hr drive in a good car and I didn't know about the chert when I was last there(not that I actually know now) :) luckily I don't need flint right now.  I'll find out though someday?

[ggraham]

Most everything we dig out of the ground around here is either flint or limestone (or oil <_<) - some areas have more of those materials laying on the surface than usable soil for agriculture.  Must have been decent material for the ancient Amerindians as the stuff is everywhere.  Walk over any plowed pasture after a rain and you are liable to find some type of flint tool or point.

 

Re the OP question; some flints are much better at throwing sparks than others.  I have found some pieces that almost look like a grinding wheel spark spray when you hit them on a steel - others might throw one or two sparks over several strikes.

I have a crushed limestone drive and as I walk it daily, especially after a rain, I am always finding "flinty" looking rock pieces, I have been carrying a steel striker with me to test, and I keep what sparks decently, no need to 'explore', just walk the side of a road somewhere crushed lime stone is used as base material, at least in Texas.

 

George

[bigfootnampa]

Here in Missouri you can walk any creek bed and pick up dozens of sparky stones in a few minutes! Cherts, cavestones, quartz and others! Back in Idaho we used to hunt where whole mountains were mostly rhyolite shale that sparks decently and was commonly knapped by the indians. Don't get hung up on flint! Hundreds of stone types can be used!

[evfreek]

Hi.  Thanks for the information.  I was trying to use the tip of the file.  Now I know that I have to use the edge of the file with the teeth ground off.  I used to have a geology pick, but lost it quite a while ago when I decided that I was not going to study geology.  I will try the striking off a hammer head as well.  I tried using a large carbon steel drill bit (no teeth), but this may have been the wrong kind of rock.

 

Doing a web search on the Indian rock drawings and Arizona flint did not turn up much.  The only hit I got was for Payson, Arizona, which is quite a distance from Four Corners.  That site had a large picture of whitish rock with red streaks, which looked a lot like the rocks I saw.

 

I will try watching that video that was suggested for finding flint in California.  I think that I may have already seen it and it did not help much.  I have some strong, hard rocks, but these do not throw any sparks.  I also have obsidian, but as mentioned earlier, this does not work.  I also have illumite, lots of carbonates like baker and baroque dolomite.  Obviously, these will not work either.

[ThomasPowers]

Drill bits are often High Speed Steel that does not throw a good spark.

 

Did you also search under jasper, chert,...all the microcrystalline quartz names?

[Charles R. Stevens]

Look up the swichboard for the state goverment, they will put you in touch with the state geologest, a local historian or archeologist can also point you in the right direction. But don't forget that flint and other knappable/strikable stones were trade goods, and may be scarce in AZ. I remember a lot of sandstome and valcanic rock, but if I remember The west side of black mountain in cave creek is eithe slate or shale.

[evfreek]

I never did find any of that odd flint that I saw at Four Corners.  Maybe later, when I go there again.

 

I eventually found some better web resources, especially a Youtube video about finding flint (chert) where it does not naturally occur.  Look at rock fill, especially near railroads.  Most of the fill rock was local.  There was a lot of basalt, and nothing like the one in the video with 50% flint!  Eventually, I found one piece in a landscape job that looked just like the example.  This worked great.  Another video recommended jasper.  But this does not have the correct fracture geometry, and requires a lot of work with the hammer to get a good edge.  It does, however, work as well.

 

The drill bit mystery was not quite solved.  Thomas pointed out that the drill bit could be HSS which doesn't throw the same kind of sparks as simple carbon steel.  Not for the bit I was using.  The tip blew out while drilling aggressively, and it turned out to be an old carbon steel drill.  It is really easy to see the difference between 1080 and HSS with a spark test, but the bit could have been 1085.  It is not HSS, for sure.  Anyway, it worked, but with much difficulty, with the correct rock.  Probably, it was not full hard, and the spiral flutes make it difficult.  I will try unwinding it and hardening it better.

 

Anyway, thanks for the help.  Flint and steel is fun.  Eventually, I'll get back to the Arizona question.  Meanwhile, the main points are:  get a smooth full hard piece of steel, and although the type of fine grained quartz sedimentary rock may not matter much, the fracturing pattern of flint really helps to get that nice edge.  Rounded rocks do not work well.  Videos help to show the striking technique.