Is this Chert?

[Missouri Mule]

I posted these pictures yesterday with some questions, but I am thinking maybe I posted to the wrong category. I know these rocks are not artifacts, but would any of you know if these rocks are chert? I realize that without being able to handle them it may not be possible via a few photos. The coffee -and- crème colored ones are shiny and appear to chip like chert, and when banged together they make a sharp noise, whereas the other rocks in the creek make a dull noise in comparison. The smaller of the brown ones has chips around all its edges, which I believe are natural, which the creek has polished smooth.
The mottled grey rock has the same characteristics as the brown ones. I believe I have seen artifacts made from similar material, but I haven’t seen any made with the brown material. Are any of you artifact hunters aware of a chert of this color or artifacts made from it?
This leads to a few last questions?
How does one identify chert? Are there books to help identify it?
In your experiences in finding artifacts have you found artifacts made from chert that comes from the exact same locale? I realize that experienced tool makers likely knew which materials work better than others and traveled or traded to get the best, but it would be fascinating to find artifacts that come from a very specific area where the chert was located.
Thanks

[Mt. Hope]

Looks like chert to me, MM

[11KBP]

Missouri Mule wrote:


  I know these rocks are not artifacts, but would any of you know if these rocks are chert?  I realize that without being able to handle them it may not be possible via a few photos.  The coffee -and- crème colored ones are shiny and appear to chip like chert, and when banged together they make a sharp noise, whereas the other rocks in the creek make a dull noise in comparison.  The smaller of the brown ones has chips around all its edges, which I believe are natural, which the creek has polished smooth. 
Thanks

  From the pictures I would guess that all three of those materials would produce conchoidal fractures. The silica content (the higher the better) will determine the knapping quality.

[Missouri Mule]

I did some digging on the Internet and discovered the "scratch test."  Using a nail or knife blade try to scratch the rock.  If it leaves a scratch mark comprised of rock residue it's not chert.  If it does not leave a mark and on light colored rocks leaves a mark comprised of metal residue especially if one uses a nail to do the test), it's chert.  I may have oversimplified it, but I think this is right. All of the rocks in the pictures pass the test as chert.  More so, I managed to find an obscure geological article that mentions "brown chert," sometimes called "Meramec chert," which is named after the Meramec River in the Ozarks. Has anyone found or seen artifacts made from this chert?  Thanks

[Bill]

The brown colored stones look like Jasper to me. I suppose you could call Jasper a very close cousin of Chert.

[greywolf22]

The yellow material is Jasper.
Jack

[Missouri Mule]

I found this on the Internet about Jasper: "Chert is the general term applied to the granular cryptocrystalline varieties of quartz, of which flint and Jasper are examples. Jasper is a variety of chert, which is the general term applied to granular cryptocrystalline quartz varieties."  Anyone ever find an artifact of brown jasper?

[11KBP]

Missouri Mule wrote:

  "Chert is the general term applied to the granular cryptocrystalline varieties of quartz, of which flint and Jasper are examples.
Jasper is a variety of chert, which is the general term applied to granular cryptocrystalline quartz varieties."

  Exactly!

[11KBP]

Missouri Mule wrote:


In your experiences in finding artifacts have you found artifacts made from chert that comes from the exact same locale?  I realize that experienced tool makers likely knew which materials work better than others and traveled or traded to get the best, but it would be fascinating to find artifacts that come from a very specific area where the chert was located.   
Thanks

  I have tried posting to this question several times but continually get an internal error notification

[11KBP]

Missouri Mule wrote:


Anyone ever find an artifact of brown jasper?

  I have found many artifacts made of brown chert (jasper), however they are not the same material as what you posted pics of.

[Missouri Mule]

11KBP . . . that's very interesting.  Could you post a picture or two of these artifacts?  All I know so far is that the rocks I posted are some form of chert, but as to what it exactly is, it still needs to be determined.  I did find some website selling artifacts purported to be made of brown jasper and the material look the same.  I always love a mystery.  Now, if only I could find an artifact from the same locale that is made from the same material . . . that would be most fun!

[Mt. Hope]

Mt. Hope wrote:

Looks like chert to me, MM

  I'm quoting myself here... :S, but I'm going to say that the chert you have found does not look like jasper, IMHO. Chert, yes.  Jasper, no.

[painshill]

It helps if you remind yourself that terms like flint, chert and jasper are not strictly speaking geological terms and certainly are no longer used as such with any universal agreement on form and composition. The popular use of the terms in a non-geological sense has been influenced more by the users of the materials than by geologists. As a general rule, geologists primarily classify rocks according to what they are – not how they formed – and may further qualify those terms with descriptions concerning formation.
On this side of the pond, we use the term “flint” for material that originated in chalk formations and the term “chert” for material that originated in limestone… but it’s cryptocrystalline quartz in both cases – or often a mixture of cryptocrystalline and microfibrous quartz in the case of chert. Beyond that, there is a spectrum of possibilities for which the distinctions are non-geological. The more microfibrous the quartz is, the more likely it is that we would term it “chalcedony”. When it has extremely high purity of silica it’s sometimes called “silex”. Jasper is essentially an opaque form of chert coloured by iron oxide inclusions.

For early Europeans, the differentiation between flint and chert embraced a difference in quality. Flint was regarded as higher quality and that’s a function of it being formed in chalk deposits with a particular geological formation history, having a particular water content and being generally derived from silica that originated from sponge spicules. In the New World the distinction based on quality was reinforced by the term “flint” being adopted to also distinguish between differing qualities of local chert. There was also a tendency to use the term “flint” to describe nodular chert (as opposed to chert in massive layers or beds), which generally reflected that same quality difference.

There is - as far as I know - only one deposit in the whole of North America that might be described as “flint” by European terminology… “Georgetown Blue” which comes out of the Austin chalk in Texas. There is also a flint-like nodular material which comes out of the Niobrara chalk in South Dakota. Other than that, flint as we would know it comes from European importation – flint cobbles were frequently used as ballast in empty ships arriving to take cargoes of tobacco, cotton and such. I have seen quayside roads in ports like Savannah, GA composed entirely of English flint.

Think of it like this. If you mixed sugar and water together and started heating it, there is a spectrum of possible end results which depends on where the sugar originated from, how long you heat it, what temperature it reaches and how much water is driven off. You might end up with what could be termed syrup, caramel, treacle or molasses. The distinctions between these arbitrary terms is not rigidly defined… we use the terms generically based on a loose classification that doesn’t have distinct boundaries.

Add in a few impurities (like a bit of milk or some butter) and the end result can go in different directions… toffee or taffy, butterscotch, fudge… dulce de leche even. Add in some ground nuts and you’ve got praline. To a chemist it would all be characterised as “caramelised sugar”.

That’s pretty much the reason why there is so much confusion in the microcrystalline quartz family.

[PS: I wouldn't be too quick to rule out the item in the 4th pic as an artefact without a closer examination of the features that bring it to a pointed end... including the side we can't see]

[Mt. Hope]

Thanks Roger for your explanation.  I recollect you having posted a similar explanation some time ago.  For me, it's sorta' hard to grasp and get a handle on it.  At this point...I'm not quite sure what it is I find.  All I know is that I like it all!!!  Mine, yours, his, hers, theirs!

[11KBP]

painshill wrote:

 
Jasper is essentially an opaque form of chert coloured by iron oxide inclusions.

  Agreed, but you will be hard pressed to get the collecting community to change their terminology, lol.
And when its all said and done there really is no harm in using the terms jasper and chert interchangeably.