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Japanese Natural Stones, their composition and character

I contributed to a thread the other day
http://badgerandblade.com/vb/showthread.php/415087-Two-french-Friends-are-visiting-me-(Hone-ID)
with this;

Sebastian
Really nice looking stones.
The red inclusions you mentioned look very familiar. I am not certain that your stone with the red inclusion is a Japanese hone but it is very similar. There is a chance that many of the natural stones that are fine enough for razors from, no matter what country' share some of the same components, that red spotting is one item on the list along with the clays and binders.

The red spots are Radiolarians and the shell that the radiolarian and diatoms leave behind are the secret cutting agent found Japanese hones and others. In Japan they call it "renge" (ren-gay) and some stones are rich with it and some are just spotted like yours. Again I am not saying that yours is a Jnat but it is indicative or late Triassic and early Jurassic sedimentary stones, an era 225million years ago that created wide groups of sharpening stones we all use no matter if they have radiolarians you can easily see or not. I have mentioned these ancient fossils in a couple of articles on my website.

Alex

A few posts further down one of our most prolific contributors added,

Alex - none of the Suita with Renge that I've owned, have had Renge that contribute to sharpening.
None. Zero. Nada.

I have had Suita Tomo --- many of them. Some with Renge on one side, none on the other.
The white side cuts, the Renge side was way less effective. That's why I started looking into this.
I do have Suita Tomo with lots of Renge that work well - but the cutting isn't from the Renge. Just happens to be a good stone.
If that stone had no Renge, it would cut much better.

I believe I mentioned that no one I've discussed this topic with - Japanese people in the trade, not forum gurus - says that Renge adds anything to the cutting power. Many have said Renge lowers the quality of the stone - I don't know that I entirely agree there - but I get their point. If the Renge isn't cutting, then the quality is lower.

As for So-sans comment, well - I'm not going to be the one to blow the whistle on that circus, but let me say this - I've taken him off the pedestal and for good reason. You might want to do some research on the topic yourself.
Just sayin', might want to reconsider your sources.


If you want to copy/paste information, fine - check out what JimR posted about on this topic.
I believe that you can find what I'm referring to in his dictionary under 'Renge'.

Japanese natural stones like we use in honing razors as the final finishing stone mainly come from a small area near Kyoto in a valley known as Umegahata, all of the stones in that area were created about 225 million years ago during the time of Pangaea when the continents were being formed. The sedimentary stone from Umegahata primarily consists of two main ingredients, mineral clays (hydrous aluminum phyllosilicates) and ancient radiolarites test fossils of amorphous silica. There may be small amounts of other minerals and oxides, many that were leached into the stone formations through ground water, but in the better stones their presence is minimal.


The radiolaria provide the grit and the clay the binders, and radiolaria come in many different colors as do the clays. The mixture of these two compounds create fast cutting stones (high grit content) or slow (high clay content) and the hardness of the stones is the result of the geological compression of the stones (deeper under ground harder, shallower are softer). Both harder and softer stones can have a higher grit content just as some harder & softer can have a lower grit content. The amount of grit was determined at the time of origin. The original creation of the stones occurred as micro size windblown dust settled into pools of ocean water that contained rich concentrations of radiolarians, and I quote Wikipedia here.

Mineralogy and Petrology[
edit]
Radiolarites are biogenic, marine, finely layered sedimentary rocks. The layers reveal an interchange of clastic mica grains, radiolarian tests, carbonates and organic pigments. Clay minerals are usually not very abundant. Radiolarites deposited in relatively shallow depths can interleave with carbonate layers. Yet most often radiolarites are pelagic, deep water sediments.
Radiolarites are very brittle rocks and hard to split. They break conchoidally with sharp edges. During weathering they decompose into small, rectangular pieces. The colors range from light (whitish) to dark (black) via red, green and brown hues.
Radiolarites are composed mainly of radiolarian tests and their fragments. The skeletal material consists of amorphous silica (opal A). Radiolarians are marine, planktonic protists with an inner skeleton. Their sizes range from 0.1 to 0.5 millimeters. Amongst their major orders albaillellaria, ectinaria, the spherical spumellaria and the hood-shaped nassellaria can be distinguished.

The stones we use called variously, awasedo or tennen toishi are the results of this ancient event, and are unique to this small 8 mile long valley in Japan. There are other unique sharpening stones for razors found throughout the world, but they are unique to themselves, just as the tennen toishi are unique to themselves and there for comparisons are problematic. The uniqueness of the tennen toishi is in the abilities of the radiolarites to breaks into smaller pieces of amorphous silica under moderate pressure while still maintaining much of their abrasive abilities. These friable silica fragments are then able to morph from an estimated grit particle size of 8,000 into smaller particles of 12k, 16k,20k and even into the 30,000 range as the abrasion under pressure continues. No other stone in the world has been found to have the same properties while containing the same higher concentration of friable silica.

As the Wiki article above states, the radiolaria can come in various colors; whitish, red, green, browns and mixtures and combinations of these colors are found in the Japanese tennen toishi. The colors of the tennen toishi are a reflection of their raw materials which are clays and microfossils, nothing much more or less. The beautiful red patterns or black patterns found in some stones are concentrations of these fossils which themselves measured in the 1 micron or less sizes. The patterns of these red radiolaria are not individual fossils but concentrations, the same as in the momji or maple leaf patterns. High concentrations of red radiolaria are just that, high concentrations of the only grit component found in Japanese tennen toishi. These red particles have the same cutting ability as the whitish or the brownish grit particles, they are all radiolarian microfossils.

With all allegorical references aside of who's stone cuts faster or better then someone else's stone, the facts of geology must prevail, some stones have higher concentrations of grit than others, period. If someone has a stone with lots of renge (red particles) that cuts slower than a whitish stone they possess, then the red spotted stone has less grit per weight and more binders. Or vise versa. The red has nothing to do with it, it is the predominance of the clays that overweigh the abilities of the diminutive amount of grit. This will be true with Arkansas or Coticule stones as well. The colors of the stones are just a cursory indicator where as the stone must stand on its own merits as to fast or slow cutting.

Your patience in reading the post is appreciated.
peace, Alx
 
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There are always going to be people that believe Renge is a superior cutting agent. Even though it isn't.

And - apparently, members of the Kyoto Whetstone Assn agree, and so do many well respected users/dealers/collectors of Jnats.
In my world - the theory of Renge being a superior cutting force is a fabrication or an assumption or both.

Claiming Jnats are comprised of radiolites isn't wrong, but lets not forget that there are other components - minerals like iron, nickel, and manganese, not to mention plant life, sea-animal remains, volcanic ash, etc. All of which adds to the 'matrix' - colors, characteristics, etc.

This could continue - we could, for example - say that if Renge was a more powerful cutter then Iromono stones must also be more powerful cutters. But they aren't.

Factually - the stones that are uber consistent, with close even and straight layers, with a lack of color variation and inclusions are regarded as the better performers.
Designs and colors are pretty, but they don't indicate performance enhancements.
 
Keith


I did not claim that the red renge particles are superior, those are your words. I only said that they are equal to the other grit particles because the renge is the same as the whitish or green or brown radiolarians that make up the bulk of the grit particles in these stones.

The minerals you mentioned are not grit and have no effect on the cutting powers of the stone, unless, and this is a major point, those additional " components - minerals like iron, nickel, and manganese, not to mention plant life, sea-animal remains, volcanic ash" overshadow content wise girth of the silica cutting particles. If the additional material like you mentioned is too great a percentage it will by defination be a silica poor stone and therefor a slow cutting stone.

Let me ask you. What is the grit component in Japanese tennen toishi? Is it silica? If so what form of silica? What is the grit component?
It is just science here.

Alex
 
Alex, So's words about Renge being superior is in your post.

Minerals and foreign matter account for many things, including color and patterns.

The predominant cutting agent in whetstones here isn't in question.
The question is whether or not Renge is indicative of perforamance and it isn't.
I'm sure you realize that not all renge is red, so the discussion is somewhat ridiculous at this point.

Similarly - not all stones with red in them, is Renge, nor is it always radiolite-based.

With this - I'm done.
 
Alex, So's words about Renge being superior is in your post.

Minerals and foreign matter account for many things, including color and patterns.

The predominant cutting agent in whetstones here isn't in question.
The question is whether or not Renge is indicative of perforamance and it isn't.
I'm sure you realize that not all renge is red, so the discussion is somewhat ridiculous at this point.

Similarly - not all stones with red in them, is Renge, nor is it always radiolite-based.

With this - I'm done.

I am still not seeing the word SUPERIOR in my postings, only yours. But I am glad that we agree upon everythng else.

I agree that the red color of aka-pin stones or other tomae type stones is not a supercharged amount of renge, and is actually oxidized minerals and metals. But the aka-pin stones, all the suita and all of the tomae no matter if they are the yellows, reds or purple varieties always have as their base cutting particles amorphous silica radiolarian. It is just that renge appears only in Suita type stones and I contend that the apperance of renge in suita stone is simply an indicator of red colored radiolarian, but not an indicator of inferior or of superior cutting, it is only the amount of grit per weight for any particular stone that affects the cutting power of any given stone.

I belive So-san was the first person to make the radiola connection known online, when he published that wonderful yet long essay on his website. He also shared this info in the knife forums freely.

Thing about Renge is this - every learned person that I've ever talked to about Jnats, Suita in particular, has said that Renge is a visual aesthetic, and has nothing to do with cutting.
Was Renge formed from radiola?
Well - if it was, then wouldnt it enhance cutting? - right? But that really doesn't seem to be the case, seems to be more of a myth or old-wives-tale really.

Many woodworkers using Suita for decades upon decades have shared with me that the fastest and best Suita are all white - and that the presence of Renge reduces the 'quality' of the stone.
Beautiful, yes - functionality enhancement - not so much.
In my own experience, I've found this to be true - the two best cuting Suita I've owned have been pure white.

best wishes,

Alex
 
I agree that many times the colors in stones can be aesthetic only. BUT that drives the price as well. I have a few "mild mannered" asagi colored stones that are great finishers. But the beauty adds to the price as the beauties are rarer even though in the end they all produce.
 

Steve56

Ask me about shaving naked!
Re:color, or not.

i tried out a karasu that was dark in the base color, and couldn't tell when the slurry got dry. Honing on dry slurry is not a good thing. There's a reason light stones bring more. Whether you want to pay for it is another question!

Cheers, Steve
 
Steve & Bill
You are correct that visuals do drive price to some extent, but that is a narrow slot in a much wider performance field of usage. I hand planed some old timbers this past week with japanese hand planes. I used a King 1k and then a dark green asagi for finishing. With tools the swarf can be seen more easily because of the volume on darker stones, but although looking at the edge from head on to the edge for a light reflection at that very last stage of honing off the burr, 4 minutes out of 5 were spent feeling the back of the blade for burr development proveing my access and beyond to the edge. I want steel removed.

We are all focused on razors here, I am too, but 99.99% of the natural stones traded in Japan for hundreds of years have been to tool people, professionals who demand performance and are heavy users, thus the grade 24 stones that are 220 x 85 x 35mm thick. Whether carpenters, umbrella makers, usushi crafts or metal workers most sharpening is done by feel. Keith is correct, the better grade of stone are normally homogenous even and dull colored stones. Even the most gifted kiita you would be surprised at how dull the yellow color really is in person.

On the forum here I read comments on how pretty a particular stone is. I want to know how fast a particular stone is. My method displays this to me directly and without back talk.

Alex
 
David

What I mean by back talk is my honing method provides me with a no frills honing experience with fewer false positive results to show me how much grit the stone has. Since I use the same forward leading stroke each time, the same general pressure, always a slurry generated with a diamond plate and a diminishing stroke count that alternates regularly from bevel side front to back my results are easy to decipher. It is about speed with me and grit content.

Sorry for any confussion.

Alex
 
Thanks for the thread and pictures Alex. Though there is a lot of interesting info here, one of the best was showing how the slurry introduced convexity to the bevel. Your photos made that very clear. I also found the composition of JNats to be very interesting. I just started playing around with some local shale that is mostly diatoms and volcanic ash.
 
Thanks for the thread and pictures Alex. Though there is a lot of interesting info here, one of the best was showing how the slurry introduced convexity to the bevel. Your photos made that very clear. I also found the composition of JNats to be very interesting. I just started playing around with some local shale that is mostly diatoms and volcanic ash.


There maybe maps of your area that show the deepest thickest deposits of those ancient diatoms that will provide a wider variety of shales for you to choose from. Good luck, keep us posted.

Alex
 
This will be true with Arkansas

Not exactly. Arkansas silica content is high enough they can be considered nearly pure "abrasive", the idea of filler or binder (or in this comparison, "clay") with arkansas stones doesn't really make sense. What determines their speed is the condition of the surface (how irregular it is) and the friability of the stone (which keeps harsher surfacing of the stone rather than smoothed or clogged stone in contact with the tool, and is why Washita's cut so ridiculously fast for an oilstone).
 
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...
... The sedimentary stone from Umegahata primarily consists of two main ingredients, mineral clays (hydrous aluminum phyllosilicates) and radiolarites (phosphoric acid calcium CaHPO4). There may be small amounts of other minerals and oxides, many that were leached into the stone formations through ground water, but in the better stones their presence is minimal.


The radiolaria provide the grit and the clay the binders, and radiolaria come in many different colors as do the clays. The mixture of these two compounds create fast cutting stones (high grit content) or slow (high clay content) and the hardness of the stones is the result of the geological compression of the stones (deeper under ground harder, shallower are softer). Both harder and softer stones can have a higher grit content just as some harder & softer can have a lower grit content. The amount of grit was determined at the time of origin. The original creation of the stones occurred as micro size windblown dust settled into pools of ocean water that contained rich concentrations of radiolarians, and I quote Wikipedia here.
...

Radiolarites are biogenic, marine, finely layered sedimentary rocks. The layers reveal an interchange of clastic mica grains, radiolarian tests, carbonates and organic pigments. Clay minerals are usually not very abundant. Radiolarites deposited in relatively shallow depths can interleave with carbonate layers. Yet most often radiolarites are pelagic, deep water sediments.

I'm a bit confused here, is this inconsistency just semantics of the subtle difference between "clay" and "mica" ?
Also, where does the idea that Radiolarites are composed phosphoric acid calcium CaHPO4 come from? Isn't the point that the radiolarian test (shell) is made of silica?
Also, what evidence is there that the red colour is anything but iron oxide?
 
I'm a bit confused here, is this inconsistency just semantics of the subtle difference between "clay" and "mica" ?
Also, where does the idea that Radiolarites are composed phosphoric acid calcium CaHPO4 come from? Isn't the point that the radiolarian test (shell) is made of silica?
Also, what evidence is there that the red colour is anything but iron oxide?
I did a little research on the phosphate and came up with nothing....
 
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