Thread: Reasons I feel hones have to be sedimentary

Well, if it's a really hard stone--much harder than steel--and pure, then won't the stone work like a diamond plate, basically? Rather than particles breaking up and doing honing, it will be a very hard surface that takes the finish that you give it and KEEPS it?

Isn't this, in fact, how the spyderco hones work?

I'm no geologist and what little I know on this topic I've learned on the forum from posts by Bart, Blaireau, and Howard among others. What Karl is saying goes along with the accounts I have read about why the coticule and the Escher families of stones cut razors so efficiently and effectively. It does seem that hones in general (naturals) are all from sedementary rock and that the synthetics mimic them in their construction. Interesting thread.

I'm not saying solid hard stones won't work, I'm just saying they'd be a pain cus you'd have to lap the grit into them, and that you would have no way of knowing what that grit is except by guess and check. And you'd have to find a way to refresh that grit, because as it seems is common sentiment, DMTs do slow down, not become finer, but become less aggressive. So if we're talking something not as hard (and therefore as durable) as diamond, something closer to steel, as say, jasper, is, it'll settle down much faster, so you'd have to keep reapplying your surface to the hone. I have to emphasize that I doubt the grit would get finer, just a lot slower. Unless it were a final finisher and as smooth as glass, in which case this is a good thing, but ultra ultra slow. Someone on B&B made a jade hone and I dunno if they realise it, but they simply just made a stone buffer. The edge they got is highly mirrored, and its very very slow. So basically its not cutting, just slowly slowly polishing. I'm interested to hear Howards take on this.

And someone pointed something out to me, as a counterpoint but I really think it is a "co-point", there are some sedimentary stones were the sediment does the cutting, there are no cutting particles, ie, Arkansas stones. I feel this happens because the sediment bond is not as good as a crystaline bond, so the pieces of sediment are continuously breaking off from each other.
This is I guess illustrated in the difference between conglomerate and say, limestone. (exaggeration, conglomerate incorporates pebble sized particles, where limestone is almost homogenously CaCO3). One is clastic sedimentary rock, ie, it has discrete particles bound by something else (see escher, coticule), the other is biochemical sedimentary rock, formed by the chemical deposition of ions coming out of solution or the breakdown of organic matter (see arkansas). Many clastic rocks have biochemical sedimentary cement, typically limestone or clay.
Typically we would be interested in Shales (escher, coticule, anything from the UK) as they are defined as clastic sedimentary rocks with a particle size less than .002 mm, ie, less than 2 microns. However, some silt stones would be fine for rougher grits, defined as .002mm to .063mm, ie 2 to 63 micron.
Now if memory serves, clasts (the particles) are typically harder rocks, typically quartz (as is the case with thuringens I believe) but also things like feldspar, garnet (coticule) corundum, etc. This mixes with a cement material (lime, oil, softer rocks that were weathered even finer, organic matter) and forms a clastic rock.
On the other hand, some rocks can form from the deposition of bio matter, then through decay, deposition and pressure, became organic/biochemical sedimentary rocks, now we have what I believe formed the J-nats and arkansas stones. I am not sure what the cutting particles here would be butting I'm guessing oxidized metals- Al2O3 and the like, maybe some silicates (SiO2). I believe most organic depositions are carbonate minerals (CO3- like chalk, limestone) which I believe is quite soft so I doubt that does the cutting. Anyway, hopefully a real geologist will chime in, this is just what I remember learning from my grandfather.

In my hone hunt, I have forgone hard minerals. I am now trying to track down where I might find quartz clasts in the shale around Ithaca. We have deep gorges (and I live literally on the edge of one) that expose hundreds and hundreds of layers of rock, so hopefully a few will be usable. We'll see. I chose quartz cus its the most common, but really any hard, fine clasts should do.

Hmm, good points Khaos!

The arkansas honning stone is one of the few natural stones out there that claim to have a progression of stones...ie., wa****a, soft, hard, true hard, black hard and translucent...they are currently graded by color and density.
They are primarily made of novaculite, whose crystaline structure is claimed, to range from 2-5 microns in size.

Based on my interpretation, of what your saying, truely the 'performance' grading should be done not only by density and color, but by the substrate(sediment) bonding material that holds the novaculite(crystaline structure) together? Since this substance is what determines how easily the novaculite crystals are released, while honing.

Most likely the density/honing capabilities, of the various stones is determined by this substrate (sediment,) rather than the novaculite itself?

Great thread, btw.

Thanks,

Mac

As far as the different colors/grades of AK stones, I suspect that the differences in color are directly related to the 'other' minerals in the stones acting as binder.

As far as the substrate being 'more' important, I suspect that it's more a matter of being 'just as' important.

Novaculite probably has a very different crystaline shape than the crystals in a coticule. (amathyst isn't it?)

Diamond, again, a completely different shape and structure.

I'm pretty sure that all of those 3 are harder then steel, but I STRONGLY suspect that if you were to make 3 synthetic hones using the exact same binder and crystals of the same size, the 3 would perform very differently.

You're on the right track I think, but you're confusing some things-

Originally Posted by McWolf1969

Hmm, good points Khaos!

The arkansas honning stone is one of the few natural stones out there that claim to have a progression of stones...ie., wa****a, soft, hard, true hard, black hard and translucent...they are currently graded by color and density.
They are primarily made of novaculite, whose crystaline structure is claimed, to range from 2-5 microns in size.

Novaculite is any siltstone (recall that siltstone varies from about 2 to about 6 micron) with that composition. Anythign smaller than 2 micron is not siltstone and therefore cannot be novaculite.

From wikipedia:
"Novaculite is a form of chert or flint found in the Ouachita Mountains of Arkansas and Oklahoma and in the Marathon Uplift of Texas. Novaculite is considered to be geosynclinal [this means that a build up of sandstone cause a sink basin resulting in the high pressure needed for partial metamorphism] highly siliceous sediments [quartz is a silicate] and may be a product of the low-grade metamorphism of chert beds. The strata were deposited in the Devonian Period and subjected to uplift and folding during the Ouachita orogeny of the Pennsylvanian/Permian Periods. Novaculite is very resistant to erosion and the layers of novaculite stand out as ridges in the Ouachita Mountains.
Novaculite is a form of microcrystalline or cryptocrystalline quartz. The color varies from white to grey-black and the specific gravity shows an increase from 2.2 to 2.5. The very hard dense rock is used as a whetstone. It has been mined since prehistoric times both as material for use as arrow and spear points and as sharpening stones.
The word novaculite is derived from the Latin word novacula, for razor stone."

My best guess is that quartz is the cutter and the chert is the cement of the stone. J-nats are also formed with chert as a cement IIRC, though I don't know what the clasts (cutting particles) are.

Originally Posted by McWolf1969

Based on my interpretation, of what your saying, truely the 'performance' grading should be done not only by density and color, but by the substrate(sediment) bonding material that holds the novaculite(crystaline structure) together? Since this substance is what determines how easily the novaculite crystals are released, while honing.

Performance is a massive coming together of cuttign particles- their agressiveness and size, and the cement- its tenacity, rate of wear, solubility etc. I feel the reason Novaculite is broken down into this or that grit by density is that all minerals have a specific density, ie, quartz will always be x g/cm^3, mica will always be y g/cm^3, and thus any variation in density is a variation of mineral content. If you really cared you could solve this using matrices but I don't really want to. For sake of argument here is an example using arbitrary numbers. Element x is a cutting particle, density 5g/cm^3. Mineral y is a cement, density 2g/cm^3. If a 10cm^3 sample is 10% cutting particle by volume, it's overall mass will be 23g (1cm^3*5g/cm^3+9cm^3*2g/cm^3), and its density therefore 2.3g/cm^3. If a sample is 20% cutting particle by volume its mass will be 26g (similar equation, substitute numbers) and therefore have a density of 2.6g/cm^3. Therefore, two samples of a rock both containing Y as a cement and X as a clast, and therefore the same type of rock, will vary in density due to the actual percent composition.
I just realised that since we dove of the cliff and are now into the nitty gritty of geology, we should differentiate rocks and minerals. Minerals are a PURE, HOMOGENEOUS substance, with a given DENSITY and set CHEMICAL PROPERTIES. Rocks CAN be pure mineral, but are typically mixes of minerals, and therefore vary based on percentage content. Granite for example, is an igneous rock containing mica, feldspar and quartz. The amounts can vary- black granite is high in mica, pink granite is high in feldspar, but they are both still granite.
Similarly, sedimentary rocks are defined by the minerals contained, but then also by the size of the particles of the minerals contained. You can have a sandstone and a conglomerate that are identical in percent composition, but are different rocks because sandstone is much much finer than conglomerate.
This is why novaculite is still all novaculite, even though the colour varies. It is a certain grit range, and specific minerals. The mineral percentage content varies, and as that varies, the properties of the rock vary, colour being the most obvious, but hardness (cutting power) and particle size (grit) vary too.

Originally Posted by McWolf1969

Most likely the density/honing capabilities, of the various stones is determined by this substrate (sediment,) rather than the novaculite itself?

Great thread, btw.

Thanks,

Mac

As I just tried to explain, it depends on both, not the novaculite. Novaculite is the name of a type of siltstone. The subrate determines how fast the stone wears (in J-nats it is hard, so they don't wear out, so the cutting particles smooth out and actually get a little finer, in coticules it is soft so slurry is easily formed and the cutting particles are released so they cut faster). The particles contained with in the substrate control the grit and speed of cutting. Diamond particles (DMT) obviously are much faster than garnet (coticule). Just as DMT C ("big" diamonds) is coarser than DMT F ("small" diamonds)

I didn't see howards input. Thanks howard. So rather than being simply sedimentary, they typically are metamorphic. But still, shouldn't they be metamorphosed from sedimentary rocks?