Making a hone

[xMackx]

How they work - garnet crystals

The stones contain a large percentage of garnet crystals. Garnet is only third in hardness behind diamond and corundum (ruby and sapphire), giving these stones their fast cutting action. The soccer-ball faceted shape of the garnet crystals provides an ideal cutting angle. The crystals cut lightly into the metal, producing very fine shavings. The garnet crystals are only 10-15 microns in diameter, and penetrate about 2-3 microns into the metal. The crystals' edges cut lightly into the metal, producing very fine shavings, while the following flat facets cut the resulting burrs (wire edges), effecting the polish or hone. All in one stroke!

The stones are quarried from 480 million-year-old grey/yellow/pink sedimentary rock which has metamorphosed from clay and volcanic ash and now contains garnet crystals. It is non-porous. Known and mined since the days of the Romans, the source of the Belgian Coticule yellow whetstone, or Stone of Vielsalm, was long thought to have been exhausted and was shut down for 50 years.

The Belgian hones (Coticule and Belgian Blue Whetstone, commonly abbreviated to BBW) are very closely related. They are mined together. Actually is is impossible to extract any Coticule without also extracting massive amounts of BBW. Traditionally, Coticules were always backed by a piece of BBW. Some bonded together by nature, but most of them glued together by man. The main reason for this is to reinforce the Coticule part with the stronger Blue stone. Nowadays, Coticules are backed with a piece of Portuguese Slate, because it is more cost-effective to use easily available slate tiles for backing a Coticule than to produce labor intensive backing stones out of BBW rocks. The BBW stones are now sold separately, because they posses honing qualities of their own. Both the Begian hones are used with "slurry" This is an abrasive milk raised on top of the hone by moistening the surface with water and rubbing it with a small piece of Coticule/BBW The slurry of the Belgian hones contains spessartine garnets. These garnets are extremely hard mono-crystals with a very typical shape.

They are hard enough to scratch steel. A slurry is not made of garnets only. It also contains water (obviously), and a great deal of phyllosilicates. Phyllosilicates are minerals that are much softer than steel. These minerals bonded the garnets together before they were abraded off the stone by rubbing with the slurry stone.
On a hypothetical note, that explains what we have found in frequent observations, small garnets can easily sink in the steel. Larger garnets can't sink so deep in the steel, because the honing pressure is spread out over a wider surface area. Try scratching a table with a spoon. Now try the same with a fork (Don't send your wife or mother to me when you run into trouble over this important experiment;-)) Back to the garnets: with the size of the segments at the garnets' surface being roughly the same, smaller garnets are less rounded than larger garnets. That makes smaller garnets more "spiky".
Conclusion: large garnets leave slightly wider but also more shallow scratches, while small garnets cut more aggressively and deeper.

Coticules contain a high concentration of small garnets (5 to 15 micron in diameter): up to 40% of the entire volume of the rock.
BBWs contain a lower concentration of wider garnets (10 to 25 micron in diameter): up to 25% of the entire volume of the rock.

That makes BBW's slower than Coticules and if we are aiming for serious steel removal during the first stages of honing, the average Coticule will perform a great deal faster than any BBW. Hence, if the choice to do serious bevel correction is between Coticule and BBW, pick the Coticule.

But there's more to the picture:
The loose garnets in the slurry also abrade the very edge, while it plows through the fluid. The thicker the fluid, the higher the concentration of garnets (less water) and the more the thinnest part of the edge deteriorates from the impact with the garnets. That is a dulling action. At the same time, the garnets remove steel from the bevel sides, which is a sharpening action. As long as the edge is not very sharp earlier during the honing process, the dulling effect is negligible, because the tip is not as fragile. When the edge becomes sharper, the tip becomes more fragile and more prone to "slurry deterioration". At a given point, there's a limit where the edge looses as much keenness as it gains. You could hone the razor into oblivion and not ever get a sharper edge than this limit. One of the advantages is that you'll never "overhone" a razor on a Belgian slurry, allegedly a common danger on synthetic water hones. With normal pressure and regular razor honing methods, we have never been able to see any evidence of "overhoning" on the Belgian hones.

At equal slurry thickness, a BBW with its lower concentration of less aggressive garnets, has a sharper limit than a Coticule.

Of course you could use thinner slurry on a Coticule, but for the inexperienced user it's still easier getting more keenness of a BBW with slurry than hitting the same level on a Coticule with thinner slurry. With experience it can be done, however, and the BBW becomes pretty redundant for razor sharpening at that point.

When no slurry is used, but plain water instead, we get a different story. The garnets remain halfway or more embedded in the surface of the hone. A Coticule with its small garnets in higher concentration offers a very finely textured surface. The BBW, having more sparsely spread bigger garnets offers a less fine surface. Both hones become very slow. The BBW becomes so slow, that it seems to loose most of it's honing qualities. It almost behaves like a piece of marble. It seems to very slowly dull the edge rather than sharpening it any further. That's why it is not recommended to dilute the slurry to plain water on a BBW.
But Coticules just keeps on going, albeit at an extremely slow rate.

No slurry, no slurry deterioration either.

Obviously the edge won't gain sharpness infinitely. As with any hone there still is a limit. That limit is defined by how deep the hone cuts in the steel. A hone that digs 0.5 micron into the steel will never define an edge thinner than those 0.5 micron. That's one good reason to use minimal pressure during the final stages of honing. Coticules on water are slow. They remove almost no steel with each honing stroke. For that they can define very sharp edges. But they are so slow that it takes ages to catch up if you weren't already at a very decent keenness when you decided to start working on water only.
A Coticule with water is a finishing hone. The majority of them can't be used to make up for much neglected keenness earlier on in the honing process.

 

[Nobody]

Mack, that's an excellent find on the report! It's one I haven't seen and reads a lot like the ones I have seen.

Compare this exerpt (I bold faced the most pertinent part of the section): GEOLOGIC FIELD GUIDE
TO THE PHOENIX MOUNTAINS,
CENTRAL ARIZONA
by
Julia K. Johnson and Stephen J. Reynolds


The Proterozoic rocks are low-grade metavolcanic and metasedimentary
rocks that mostly dip steeply to the southeast (Fig. 2) and strike approximately N30
°E;
they locally are intruded by diabase dikes. In the northwest portion of the range, the
rocks are generally of submarine origin and contain greenstone intermixed with
ferruginous quartzite, as well as meta-mudstone high in the stratigraphic sequence (Fig.
3). Rocks that are more continental, including abundant sandy quartzite, conglomeratic
quartzite, tuffaceous phyllite, and metarhyolite dominate the southeast part of the range.


I'd swear I read some snippet that described spessartine involved in Ardennes coticule as being a bit softer than quartz, being 6.5-7.0 on the Mohs scale, but can't lay my finger on it. Could be I am disremembering. Dismembering? However, garnet is not necessarily the 3rd hardest natural material behind diamond and *may* be less hard than quartz or harder. Guess it depends on the composition and those details aren't at hand. Anyway, separating fact from propaganda on how coticule does or doesn't work isn't on my agenda. Locating some locally, if it does indeed exist, is. Barring that, some other examples of hone worthy stone will do nicely.

http://www.reade.com/Particle_Briefings/mohs_hardness_abrasive_grit.html

Material	Mohs' Hardness
Alumina (Synthetic aluminum oxide)	3.4
Aluminum oxide	9
Alundum (Fused brown Al[SUB]2[/SUB]0[SUB]3[/SUB])	9.0
Amalgam	4 - 5
Anatase	5.5 - 6
Apatite	5
Barium sulfate	3
Boron carbide	9 - 10
Burundum	9+
Calcite	3
Chalk (calcium carbonate)	3
Chrysoberyl	8.5
Copper slag	7
Corundum (Natural aluminum oxide)	9
Crystolon (SiC)	9.0
Cuttlebone	7
Dentin	3 - 4
Diamond	10
Diopside	5 - 6
Emery	7 - 9
Enamel	5
Enstatite	5.5
Feldspar	6
Fluorite	4
Furnace slag	7
Garnet	6.5 - 7.5
Glass Bead	5.5
Glass (lead free)	7
Gold	2.5 - 3
Gypsum	2
Hematite	5.5 - 6.5
Kyanite	4 - 7
Magnetite	5.5 - 6.5
Olivine	6.5
Orthoclase	6
Petalite	~ 6
Plastic media	3 - 4
Porcelain, feldspathic	6 - 7
Pyrite	6.5
Pumice	6
Quartz (Silica sand)	7
Serpentine	2 - 4
Silica sand	6 - 7
Silicon carbide	9 - 10
Sillimanite	6 - 7
Soda (Sodium bicarbonate)	2.5
Specular hematite	7 - 7.5
Spinel	~ 8
Spodumene	6 - 7
Staurolite	7.0 - 7.5
Steatite (Soapstone)	1 - 2.5
Steel grit	RC= 42 - 62
Steel shot	8 or RC= 42 - 50
Strontium titanate	5 - 6
Talc	1
Topaz	8
Titanium dioxide, Anatase	5.5
Titanium dioxide, Rutile	6.5
Tungsten carbide	9
YAG	~ 8 1/4
Zinc sulfide	3
Zirconia	8
Zirconium silicate (Zircon)	6.5 - 7.5

Interesting to note that steel shot are rated at "8". I wonder what is so special about steel shot?

 

[xMackx]

RELATIONSHIPS OF COTICULE GEOCHEMISTRY TO STRATIGRAPHY
IN THE PERRY MOUNTAIN AND MEGUNTICOOK FORMATIONS,
NEW ENGLAND APPALACHIANS
​

JENNIFER A. THOMSON§
Department of Geology, Eastern Washington University, 130 Science Building, Cheney, Washington 99004-2439, U.S.A.

ABSTRACT
​

Coticules (garnet-rich quartzites) are chemically distinctive lithologies of controversial origin. They generally occur in pelitic
schists, amphibolites, cherts, and quartzites as thin layers or discontinuous lenses in Paleozoic formations in the New England
Appalachians and other orogenic belts. Geochemical data were collected to characterize coticules and their host rocks from the
Middle Silurian Perry Mountain Formation of southern New Hampshire (near Rochester) and western Maine (near Rangeley),
and the Cambrian Megunticook Formation of coastal Maine (Camden and Calais). Relative to their host rocks, the coticules are
enriched in Fe, Mn, and P, and depleted in Ti and alkalis. Electron-microprobe analyses of garnet show higher spessartine and
lower almandine components relative to garnet in the host. Coticules are light-REE-enriched and heavy-REE-depleted. They have
concentrations between 10 and 100 times those of chondrites, generally lack a Ce anomaly, and have a negative Eu anomaly.
Major-element compositions and REE profiles argue strongly against a hydrothermal origin for these rocks, and do not obviously
support a hydrogenous (diagenetic) origin such as Mn–Fe formation. Rare-earth-element patterns differ as much within a local
area as for widely separated samples within a single formation. All three samples from the Megunticook Formation are nearly
identical, supporting stratigraphic correlation. But they are also like some of the Perry Mountain Formation samples, so that
coticule compositions for a formation are not unique.

INTRODUCTION
​

Coticules, or garnet-rich quartzites, are distinctive
lithologies of controversial origin. The term coticule is
primarily a field term used to describe fine-grained garnet-
rich quartzites. Such rocks are typically richer in
manganese than average pelite or shale, and thus commonly
contain spessartine. They occur in sequences of
pelitic schist, amphibolite, chert, and quartzite as thin
layers or lenses in formations of Cambrian to Devonian
age throughout the New England Appalachians and into
Newfoundland. Individual coticule-bearing formations
are continuous or nearly so along strike for distances up
to 350 km.
Historically, coticule geochemistry has not received
significant attention in the literature. Early papers primarily
focused on detailed field and petrographic descriptions,
with few data on mineral compositions and
essentially none on whole rocks. Whereas most authors
would agree that manganese is derived from a sedimentary
precursor, a variety of protoliths have been proposed:
Mn-rich sandy layers (Clifford 1960), impure
manganiferous chert layers (Renard 1878, Emerson
1898, Schiller & Taylor 1965, Eusden et al. 1984,
Thompson 1985), Mn-carbonate concretions (Woodland
1939, Bennett 1989, Schreyer et al. 1992), and manganiferous
sediment with volcanogenic affiliations (Kramm
1976, Lamens et al. 1986, Krosse & Schreyer 1993).
In this paper, I present new major- and trace-element
geochemical data for coticules from the middle Silurian
Perry Mountain Formation of southern New Hampshire
and western Maine and the Cambrian Megunticook
Formation of coastal Maine. Results of electron-microprobe
analyses of coticule and host-rock garnet also are
presented. The goals of this paper are to evaluate (1)
major- and trace-element compositions and rare-earth
element (REE) patterns for these coticules and their
possible use in protolith determination, and (2) the possibility
of using these data as tools for stratigraphic correlation
of coticules over short and long distances.

If you would like to read this book Jeff here is the link, good read: http://rruff.geo.arizona.edu/doclib/cm/vol39/CM39_1021.pdf

 

[Nobody]

Believe me Mack, I've sifted thru that one and several others with a fine toothed comb more than once. That's when I started realizing there were similarities between the strata in the different locations.

It was a reference to spessartine garnets in quartzite locally that got me looking. Turns out it's pretty difficult to find data on any related petrographic analyses. I'm pondering the possibility of contacting ASU to see if the author of the earlier report is yet in their employ. The geology department at ASU has a decent reputation but I seriously doubt that much effort has been done on the constituencies of all the non commercial rock around here. And yet, who knows what mysteries may lurk in the bowels of ASU?

 

[xMackx]

Yeah after doing a lot of reading i realized that I wasn't defining my answer to what to look for in rocks. That sub-categories or sub-groups fit the description better than the basic rock groups. That good whetstone material only comes from two groups, a basic classification of sedimentary. Another called metasediments which the coticule would be classified, which is sedimentary rock that has only gone through light stages of becoming metamorphic. Even though metasedimentary rocks are rare when it comes to whetstone material I feel simple information like this narrows down what to look for and your chances of a certain percentage of the rocks we pull out will be more likely to have preferred characteristics.

Even then where ever we live in the U.S. our best stones will probably be sedimentary. Unless you are lucky enough to live near an extinct/dormant volcano, and even then it has to be a specific stratovolcano eruption. But then again there have been large enough volcanic eruptions that have coated the entire earth in the past so you never know what you may find. Nature is known to provide the rarest of things if the settings are right.

I found a neat geological list of metasedimentary rock in all states of the U.S. http://tin.er.usgs.gov/geology/state/sgmc-lith.php?code=5.2

 

[Nobody]

I see the USGS is doing a bang up job. AZ isn't even listed tho we have some of oldest rock of that sort. Doesn't surprise me at all. The "experts" never have all knowledge, especially when it comes to minerals and such and there is a larger gap of info when it comes to common rock in any locale. But I bet dollars to donuts almost ALL of the strata around the copper producing areas have at least been looked at pretty carefully. Of course, a geologist employed by a mining concern would only think of a 10ft thich vein of coticule as "overburden", to be removed to get at the "valuable stuff". The info never hits the public domain either.

Incidentally, I don't understand why you keep focussing on sedimentary rock. The majority of natural honing stones I am aware of are metasedimentary or the like. Slate, coticule, phyllite, novaculite, all metasedimentary.

 

[xMackx]

If you reread my first paragraph in my last message that was my point, good whetstone is either going to be sedimentary or metasedimentary. The rocks have to be homogeneous in color. Which means also homogeneous in mineral composition to have a consistent abrasive cutting quality aslo qualities found in sedimentary and metasedimentary rock. I focus on it because it helps rule out a large majority of stone.

 

[Nobody]

Ahhhh, I see. I just tend to draw a greater distinction between sedimentary, metamorphic, and igneous. To me, calling a stone metasedimentary muddies the water somewhat even tho it is more descriptive than just calling it metamorphic. Both are certainly correct. The prefix "meta" in metasedimentary is certainly a small portion, but also the vital descriptor. I had a conversation with the lapidary about metamorphic stones that just didn't end until the meaning of "morph" was brough into play.

 

[Pkrankow]

If you reread my first paragraph in my last message that was my point, good whetstone is either going to be sedimentary or metasedimentary. The rocks have to be homogeneous in color. Which means also homogeneous in mineral composition to have a consistent abrasive cutting quality aslo qualities found in sedimentary and metasedimentary rock. I focus on it because it helps rule out a large majority of stone.

Now homogeneous consistency I can accept, but homogeneous color has been proven otherwise already by the results in this thread, as well as historic hones including Belgian Coticule and Arkansas novaculite, both of which are know to have speckles, streaks and other visual flaws.

I will agree that the tendency of higher grit polishing stones is to have a clear color vs streaks or speckles, as noted with translucent or black Arkansas novaculite, Cnat, and other slate finishers, but again this thread has a number of stones that are decidedly NOT homogeneous in color filling the role of finisher.

Low grit stones have no need of homogeneous color, and high grit finishing stones don't either. They need a homogeneous texture and consistency, however that is also not truly necessary since portions of the stone can be along for the ride, so to speak, and have little or no cutting action while portions have consistent smooth action.

Phil

 

[PapaFish]

I think what Mack had meant on homogenious color has merrit to it. I have a couple stones that vary in color quite a bit, and there is a definite difference between honing on one color vs. another. My Lizard Stone for example has a large green area that will hone ok, but never get me a shavable edge, it has a white edge on the top, and if I am very careful (since it's so narrow), that part will get me further along. My Home Depot slate is multi colored, and seems to cut differently according to the colors of the layers. All the layers are fairly close in finish, and none of them are good for using as a finishing stone, but it does illustrate the point. I could see some sedimentary rocks having, let's say, 5 layers of very nice tan 10K abrasive, and then a layer of black 2K, going basically 5 layers to one. (Think edge grain/end grain vs. face grain) Even though the majority of the stone is 10K, it will leave the edge of a 2K stone, but cut at 1/6 the speed of a 2K stone made only of the black stuff.

 

[xMackx]

I was just speaking from what I have learned lately and there is always room to learn more when it comes to this stuff. But I know what you mean Jeff with the "morph" part because we are dealing with sedimentary rocks that have gone through a change or metamorphosis. The stone may have started as being sedimentary but through geological processes, be it pressure over time and mineral absorption to metamorphosize a difference in microcrystalline structure. What I meant about homogenious color seems to hold true when it comes to the grading of stone and companies. Like the Escher stones were graded on color from grey to blue green, and coticules being graded from a more plain yellow to the mixed yellow grey high end finishers. To me the color reflects the mineral composition, just a thought.

 

[paco664]

anybody found anything new lately??

 

[PapaFish]

I finally got my Slate and Oil Shale lapped up (that I had gotten over the holidays). The slate is a bit disappointing. It does alright, but is definitely not a finisher. It is just a HAIR better than the Lizard Stone, but not near as good as the Wonderstone. Shaving with it feels like pulling each hair to the point it ALMOST comes out before it cuts. The edge is very consistent, so I doubt there is any chance of improving the edge I get. It would make a good intermediate hone. I am sorry, I don't know the kind of Slate it is, more black/grey than the brown stuff I got at Home Depot, and leaves a more refined edge. The Oil Shale will be the next to try. It is a whole different animal all together (and smelled terrible when lapping). It lapped quickly, and made a VERY slick slurry that impeded further lapping action. Both the Slate and Oil Shale were lapped up to 1200 grit. I will let you know what I find with the Oil Shale when I hone with it and try it out (but I expect it to be below the Slate in quality).

 

[Nobody]

Papafish, you may want to polish the lizard stone up really high and try it as a finisher. Won't have any cut, but can leave a nice edge. The scrap I have is positively glassy. Took quite a bit for it to arrive at that state.

@Paco: New? Oh..... Igor II is almost ready to try. Used a polyester resin and for whatever reason the catalyst failed completely to act. It's taking forever. Blasted thing has been out of the mould for several weeks now.

Still waiting for the damnable lapidary to make just ONE cut on the reddish stone. All I get are one excuse after another. That's the last for this lapidary! I mean jeez louise, over a month to make a simple cut that will take 5 minutes? The next meeting may be quite unpleasant for someone besides me.

Handed off a piece of stone that resembled a relative of coticule weeks ago to Pkrankow, but haven't heard anything back. It roughly matches the description given in the notes for the strata, but I haven't a clue if it is actually coticule or a close relative. Does appear to be a form of quartzite at least and hones a touch "softer" and slower than the coti I have on hand, seems finer too. Needs someone with more coti experience than me to work with it and try to make informed evaluations, so off to Phil it went. I owed him one big time.

 

[Pkrankow]

OK, I'll play with that stone more. I also got a new La Verte coticule, and lapping film....honing overload!

My initial impression is that the slurry breaks down quickly, and does not cut fast for very long. This leads me to believe that it does not have garnet in it. I think it is a promising stone, but I have not finished lapping it yet, there is still a divot in the center.

Phil

 

[Nobody]

LOL Honing overload. Yeah, I've been there. No pressure Phil. You get there when you get there. FWIW I am guessing the stone may deviate considerably from coticule in some ways. Turns out Belgian coticule is indicated to be no more than 488 million years old and the one I sent is over 1,600 million years old. The mottled reddish stone seems to show that the strata underwent more than one episode of metamorphosis too with well healed cracks along with later ones. I wish there was some way to get the stones professionally examined without costing a boatload of money.

 

[Pkrankow]

I am a lapping fool today.

I should have gone after the petrified/permineralized wood Nobody cut for me, but forgot. My sample has so many internal flaws I doubt its value as a hone, so I am just prettying up for display what I have.

I whipped out the Permatex Valve Grinding Compound and a piece of Vinyl Composite Tile (VCT flooring) and went hog wild on the mystery stone that Nobody sent me. In about 20-30 minutes the stone melted away taking most of the horrible cutting job with it. I took off about .010 inch easy. There is still a line that I am not too concerned about left, about 1 inch long and 1/8 inch wide and fairly deep (maybe .030 inch) the circled black mark is the deep spot, it is black from pencil. WOW! I wish I did this when I first started lapping on this stone. I also worked on my C-nat and can tell you this is the bomb for bulk stone removal!

...but not for surface finish. The loose abrasive creates an even texture of overlapping pock marks. I am afraid to hone on it until I lap with some sandpaper.

The Permatex compound is about 200 grit, give or take, and sticks readily in the surface of the VCT, but not permanently. I noted that on heavy paste the stone would dish slightly with the center wearing slightly faster than the edges, since material stayed under the stone. On thin paste the grinding compound would move out from under the stone and no lapping would occur. Finding the correct amount of "wet" is necessary, and changes as swarf (is that the right word?) from the stone being lapped builds up. A few drops (literal drops) can be the difference between too thin and too thick.

I have some photographs of the mystery stone and the cnat after lapping, and a surface of the cnat that was lapped to 400 grit (side surface, so it is the skinny surface).

I'll post some pictures of both after lapped with 220 grit paper, and higher if I go there. apologies about the poor photos, this is the best macro camera in the house, and I didn't take the time to set up a "proper" light box. Apologies for the dirty dishes too.

Phil

 

[Pkrankow]

Lapping fool part 2

I went to 220 grit sandpaper to finish. The cupping I noted on lapping compound was much much less as my grids came off evenly and quite quickly, though edges first on the first grid.

My cnat still has a slight hump to it, so I either removed less than I thought, or I wasn't keeping it flat...I only went at the lapping compound a few minutes. The funky texture was mostly removed rather quickly too.

Pictures!
I tried to catch the lather for Nobody, this mystery stone really raises a froth, but it is short lived.

I did walk the river today with my daughter and picked up some possibilities. Gonna be a while though, and I am not confident they will be finishers...but that is OK. No pictures today of those though.

Phil

 

[Pkrankow]

Tried honing on this mystery stone. I glass dulled a known good blade, and raised a slurry, which took a WHOLE LOT MORE effort than my first trials of this stone. The cutting sensation was through the roof this time. I think I either need to work with or on this stone more, or ... something. I thought I got the bevel back, as I have HHT1, violin, but it won't take arm hair. I will start over again and see what happens. I may need to lap the hone further because I have not gotten some of the pits out from the lapping compound. My initial evaluations were more promising that what I am getting now.

Phil
PS: Nobody, Sorry that my "tomorrow for pictures" ended up a month!
pps Nobody, as mentioned earlier my hands are again all dried out like I was working with concrete or something bare handed.

 

[xMackx]

Tried honing on this mystery stone. I glass dulled a known good blade, and raised a slurry, which took a WHOLE LOT MORE effort than my first trials of this stone. The cutting sensation was through the roof this time. I think I either need to work with or on this stone more, or ... something. I thought I got the bevel back, as I have HHT1, violin, but it won't take arm hair. I will start over again and see what happens. I may need to lap the hone further because I have not gotten some of the pits out from the lapping compound. My initial evaluations were more promising that what I am getting now.

Phil
PS: Nobody, Sorry that my "tomorrow for pictures" ended up a month!

My initial evaluation of a stone is always better too lol. Just re-read my first evaluations of any stone on here lol. I think it's the excitement of trying a new stone we made ourselves. I have only had one stone so far that an edge benefits from using it, but the more types of stone we don't succeed with just helps narrow down what to look for. That brown stone looks really beautiful Pkrankow.