David was nice enough to send me one of the white slate-backed vintage stones that people often assume are reform coticules. I'm going to be doing significant testing on it and posting findings here. Tonight's the very beginning.
Slurry tests.
Coti
This stone
This stone (thinned so larger particles are move evident)
Draw your own conclusions here, but as for my opinion. Garnet size varies quite a bit in coticules. Some of my nicer vintages garnets are very small compared to some other coticules I've owned, but the particles in this stone on average, are in my opinion, far too small to be coticule garnets. Now, there are larger particles which could be, but they comprise an insignificant amount of the stone, AND (this is important) these particles are found in almost any synthetic. It's not at all uncommon to find particles as large or larger than coti garnets populating even modern synthetic stones slurries... they simply don't tend to comprise a large portion of the slurry. As for an assumption, I would say we can conclude that IF this stone contains coticule dust, it is either a very small portion of the make-up, or the dust is lower in garnet concentration than we would expect based on the concentration in whole coticule stones. I would further say, that this test offers no proof that there are garnets in the stones, it only fails to fully disprove this.
More testing will come, honing, attempts at dilucot, and shaves.
Slurry tests.
Coti
This stone
This stone (thinned so larger particles are move evident)
Draw your own conclusions here, but as for my opinion. Garnet size varies quite a bit in coticules. Some of my nicer vintages garnets are very small compared to some other coticules I've owned, but the particles in this stone on average, are in my opinion, far too small to be coticule garnets. Now, there are larger particles which could be, but they comprise an insignificant amount of the stone, AND (this is important) these particles are found in almost any synthetic. It's not at all uncommon to find particles as large or larger than coti garnets populating even modern synthetic stones slurries... they simply don't tend to comprise a large portion of the slurry. As for an assumption, I would say we can conclude that IF this stone contains coticule dust, it is either a very small portion of the make-up, or the dust is lower in garnet concentration than we would expect based on the concentration in whole coticule stones. I would further say, that this test offers no proof that there are garnets in the stones, it only fails to fully disprove this.
More testing will come, honing, attempts at dilucot, and shaves.