Carolina Rhyolite

[Bill]

Hi Cliff, the high quality transulent green stone you mentioned is actually a sedimentary rock that has been identified by Geologists as Green Silicified Siltstone. It is chert-like in workability and some awesome points have been found that were made out of it. Years ago I saw an incredibile Hardaway Dalton that, long ago, had been found at what is now the Town Creek Site.
There is another green translucent stone that has frequently been found in Stokes County, NC,and it is Moss Agate.
Picture from left to right, Hardaway Dalton, Hardaway side notch and Kirk Corner Notch; both Hardaways were made out of Moss Agate and the Kirk was made out of Green Scilified Siltstone. I took this picture in bright light to show the greater translucency of Moss Agate when compared to Green Scilicified Siltstone. GSS has the translucency of high a quality Chert (Calcedony) and the Moss Agate is extremely translucent like a high quality quartsite.

[JoeM]

Cool guys, glad you enjoyed looking at some NC Slate Belt rock!
The varieties are many.
Yes, Hoss, Rhyolite is harder to knap than a lot of flints, cherts and obsidian.
Your knapper friend was exactly right when he said he had to use a little more force.
That's generally the case. There are super fine grades of the material that will work like "butter"
but they are hard to find. Your average and lower grades material will take a little more "umph".
A lot of types will work easily from one direction and do nothing but hinge in the other. That's
why there is really no sense in "slabbing" preforms of Rhyo for knapping like you can lots
of other materials. You really have to start from the beginning and work with the grain or flow
of the rock.
Most of the good knappers I know of in NC can't stand to work the local stuff, but they all say it's the
best stuff to learn on. Now there are a few guys that are expert with Rhyolite, love it, and don't
work anything else. They do it mainly because other knappers say it can't be done, and believe you
me, they can do it! One interesting thing about Rhyolite that all the guys that become good at
working it say is, you have to use a wooden billet to master the material.
I am not a good knapper. I enjoy seeing how good and thin of a biface I can make, just to get to
know a rock type, but have no pressure flaking technique and rarely ever finish a point.
I'd say 97.5% of all knappers these days use copper. I like to keep it abo and use only rock, wood,
and antler. Interesting too is that the guys that have become good at working Rhyolite don't use
copper either.
You're always on the lookout for good hammerstones because they wear out and break, but for bustin'
into the larger pieces pictured above, I use a regular ol' 4 lb sledge hammer to get going. Doing
it all with hammerstones would be a lot of work and a lot of stones. It's always been surprising
to me the absence of hammerstones, whole or broken, at quarry sites. You would think the ground
would be covered with them but, in my experience, they have been rare.
The black rhyolite of Virginia and further north is even harder to work than what we have in NC.
We Will Always Remember,
Joe

[Bill]

Joe, are you sure that Virginia black stuff isn't Kanawha Chert? The source of Kanawha is the area around Charleston West Virginia.

[JoeM]

Hey Bill, Our posts must've overlapped, Sorry,I didn't see yours until now.
That's a really nice Trio of points! The agate ones are beautiful for sure, but I just love that
GSS and the look of that Kirk! Great pieces!
And you are right about the GSS. That is a very high grade material. Like to find a nice vein of it!
I know there's Kanawha Chert and Black Rhyolite but wouldn't necessarily be able to tell
one from the other. Not much experience with either material.
Joe

[Hoss]

Hey Butch you started this and a very interesting thread it is turning out to be. Thanks for all that you do!

[CliffJ]

Bill wrote:

Hi Cliff, the high quality transulent green stone you mentioned is actually a sedimentary rock that has been identified by Geologists as Green Silicified Siltstone. It is chert-like in workability and some awesome points have been found that were made out of it. Years ago I saw an incredibile Hardaway Dalton that, long ago, had been found at what is now the Town Creek Site.
There is another green translucent stone that has frequently been found in Stokes County, NC,and it is Moss Agate.
Picture from left to right, Hardaway Dalton, Hardaway side notch and Kirk Corner Notch; both Hardaways were made out of Moss Agate and the Kirk was made out of Green Scilified Siltstone. I took this picture in bright light to show the greater translucency of Moss Agate when compared to Green Scilicified Siltstone. GSS has the translucency of high a quality Chert (Calcedony) and the Moss Agate is extremely translucent like a high quality quartsite.

Hi Bill,
  Yes, that nice Kirk is made of the green material I was speaking about. Out of thousands of finds I've only found a few artifacts made of that fine material. It must have come from a small limited outcrop.  It doesn't show much patination at all. I've always thought of it as a high-grade rhyolite but the silicified siltstone title makes sense. Now, is the high-grade grey colored lithic also silicified siltstone- the one translucent on the edges?
  I can't see enough of the other 2 points because of the glare- but they look much different from the moss agate I've found, which is blue-yellow with moss specks in it. We don't see much of that either.

[Butch Wilson]

Hoss wrote:

Hey Butch you started this and a very interesting thread it is turning out to be. Thanks for all that you do!

Hoss, this one has progressed way beyond me. I am "just holdin' on" and learning a lot. I love it when these guys get together and share their knowledge ! I am truly grateful.
Butch

[JoeM]

Well guys, I'm not a geologist so I don't know if I should even try and give my take on the
Rhyolite vs. Siltstone terminology, but what the heck. :dry:
Ofcourse, you have to take each specimen individually on it's own attributes, (and given the fact we
"locals" call everything Rhyolite), because of the way the rock was formed I accept either
High-Grade Rhyolite or Silicified Siltstone.
Many of the Rhyolite Formations we have in NC are Rhyolitic Tuffs. Tuffs are formed by layer upon
layer of volcanic ash. These layers, one on top of another "bind" together by different processes.
Layers that bind soon after depostion from heat are Tuff rocks and would be considered Igneous.
Layers that took a long time to "compact" or ash that landed on the surface of shallow pools of
water and then settled out, would be called Tuffaceous MetaSiltstone, or Sedimentary.
I don't think the reason the material is so hard to come by because there was only one source.
It probably formed in several places but in very thin and relatively small layers or beds.
We like to call it all "varieties" of Rhyolite, but when you get right down to it,
that ain't exactly correct. A lot of our beloved Rhyolite is actually some MetaSedimentary
MetaSiltstone. Although we do have igneous "Flow-Banded" material as well.
All the rock of the Carolina Terrane has been metamorphosed, so that makes it even harder to give it
a name. I have to quote local NC State Geologist Edward Stoddard,
" If asked whether any particular rock sample from the region is igneous, sedimentary, or
metamorphic, perhaps the most correct answer is "Yes"!"
Going to have to try and take some decent pics of the different layering.
Joe

[Bill]

Cliff and Joe, I agree that the green Silicified Siltstone must have been pretty rare. The Paleo Americans made use of the stuff because I am fairly certain the Capehart Clovis was made from it as well as a killer Hardaway or two. The Kirk people also found some of it as did the Woodland people because I found an eared Yadkin some time ago in a field.
I have re-photographed the points in less light. The Moss Agate is so translucent that I had to turn all direct lighting to make the points made of it easier to see. The Kirks and Hardaway Dalton were found in North Carolina and were made from GSS. The Hardaway Dalton and Hardaway Side Notch were made of Moss Agate and are North Carolina finds. Both points are a very pale green color (in the light).
Whoops,I just re-examined what I thought was an Eared Yadkin and discovered that the base is ground and that means that it's a Palmer. When I found it (around 12 years ago!) I just assumed it was an Eared Yadkin. I'll take a picrure of the point because it was made out of GSS.

[Weepingeyegorget]

That stuff is just beautiful.. Green is my favorite color in points!! Very, very nice color.. And I love moss agates to.. pretty!

[Bill]

Hi Joe, both you and Cliff know your NC rocks very well.

[JoeM]

Bill, That's got to be the prettiest collection of the GSS I've ever seen! :woohoo:
Thanks for the pictures. That material really sets itself apart with the lack of patina/oxidation.
I was looking thru the collection today for some of it. I found some greens that I was thinking
were close to the same material, but that's all they were, close. I will have to start looking
more closely, but I doubt I'll find much of it.
I know you can't see much from this picture,(the points are behind glass), but I think the little
Palmer in the middle of this frame is the right stuff, just maybe a lower grade.
Franklin Co., NC.

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Your three are just awesome! I would LOVE to find a vein of that stuff!
I can begin to see some dark inclusions in the agate ones but it's hard to see how translucent
they are. Thanks for the pics of two more rare beauties!
Joe

[Bill]

Those are some nice points Joe and I think the Palmer was made from GSS. I have found it interesting that from what I have seen, the higher quality the lithic the more resistant to weathering it is. However, even this could never be a hard rule because it depends upon whether the artifact weathers in acidic or basic soil. Sometimes Green Silicified Siltstone patinates lightly with not much color change at all and sometimes it has formed a white crust, indicative of heavy weathering. I believe it depends the acid-base content of the soil.

[shartis]

Interesting tread and some nice points. Thanks for all the info. A couple I think are GSS found in York County S.C. One or maybe two of the scrapers I think are GSS and the broke ear of a Hardaway. One of the woodland camp sites I hunt in Chester has some GSS on it to but not much. My brother found the Dalton that may be GSS

[JoeM]

Yep, it was inevitable. This is where it gets interesting, confusing.
I have always considered the GSS that Bill posted perfect examples of to be a high-grade of our
"Rhyolitic" siltstones, but now I'm not sure. It may be it's own animal. And where do you
draw the line?
Those are some beautiful artifacts, and great examples of material types, Shartis.
Like Bill was saying, it seems the higher grade materials do not weather or oxidize as quickly
as lower grade materials, but then it also depends on many other factors such as the acidity of
the soil it has been sitting in for the last thousands of years and the chemical composition of
the rock to begin with.
The bottom scraper in your first pic, the beautiful little bifurcate, and the Dalton are all close
candidates for the GSS, imo. Of those three, I'd say the little bifurcate is closest.
The main point or distinction that I think needs to be made is the fact that ALOT of what we call
Rhyolite is infact a sedimentary formation, making the use of the name Rhyolite generic at best.
Rhyolite is an igneous rock, A magma or lava that sometimes will exhibit flow-banding.
The "Rhyolite" formed by layer upon layer of ash is really something else but for the sake of
simplicity, we have always called it Rhyolite too.
Here are some pics of different types of our sedimentary "Rhyolite". The 2nd and 3rd have pieces
I polished. And the second type, I think, is similar to what the Guilford Butch posted a pic of
is made from.

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Now it's hard to explain why some of the black scraper material Shartis posted isn't oxidizing.
Just a higher-grade material or has it been in a non-oxidizing environment?
Anyway, I was looking for something similar to the GSS.
This is sedimentary also. Maybe a thicker layer of ash? But it will oxidize given enough time as
can be seen by the chalky cortex on this piece.

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Sometimes the thin layers are the best material. No banding, just a homogenous layer.
Here's a blank I knocked out of such a layer.

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Side view to show total thickness of layer. There is still cortex on top and bottom of blank.

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But still not anywhere close to the GSS. So here's a piece that looked like it was getting closer.
The little bit of color showing thru looked close to the GSS, but I am imagining that the GSS forms
in layers not as thick as this. (Just guessing.)

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Since you can't see much of this material from the outside and it just happens to be resting
on top of a perfectly good hammerstone, let's take a closer look.

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It's closer to the GSS, but still a ways to go.
So, a lot of our Rhyolites are Meta-Siltstones. When you set examples side by side the line between
them can get very blurred. To answer all the questions you have to do chemical and petrographic
analysis, and even then you may not be able to answer all your questions without seeing where the
rock,(layer), was formed.
As I said, I have always lumped the "Rhyolitic" Siltsones together, but after seeing Bills' beautiful
examples, I am going to have to take a closer look. I'd still love to find a vein of it to whack on!
I was putting that last piece back together and a little "tool" fell off.

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But, All better now.

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And we haven't even gotten into the "true" Rhyolites yet! hmy:
Joe