Water Erosion Or Human Influence?

[PrettyOkay]

Found along the Similkameen river in southern British Columbia. My grandfather put forward the notion that it was used to sharpen arrowheads..

Thoughts?

[Geologyhound]

How big is it?  The right size to be comfortably held in one hand?  
The color banding makes me think it might be a piece of gneiss.  Such marks could be a form of chatter mark from a glacier.  

They all are perpendicular to the grain of the rock.  I am not a flint knapper, but my knee jerk reaction is you might want to sharpen with the grain?  One of the marks (second from right) appears to extend as a longer fracture into the rock.  This suggests the feature may be pressure-derived.

There appears to be a lighter colored layer on that side of the stone.  All the marks are contained in that lighter layer except the deeper fracture mentioned above.  

I can imagine sharpening activities might dislodge grains of a sharpening stone which would result in unevenness on one side of a slot.  But, some of those slots appear to be curved.  That should not result from sharpening.  

So, my initial opinion is the marks may originally have been naturally occurring. Could some of the straighter marks have been utilized by an opportunist to sharpen?  Possibly.  I am a geologist, not an artifacts expert.  You might want to take my opinion and ask an artifacts expert at a local university.

Any flint knappers want to chime in here?

[jasong]

That looks natural to me too, for many of the reasons already stated by Geologyhound. Also agree it's something metamorphic, and appears to be a crack filling, but that I'm not certain of, especially if it's a gneiss or mylonite. 

 Not sure if the "slots" are differential weathering or some sort of cracking due to stresses (physical deformation, differential cooling effects, etc).

Leaning towards cracking though, and would guess from heat/cooling where the whole thing was heated and the central "vein" part cooled at a different rate than the outer material and caused internal stresses and thus the cracks. Potentially in unison with existing physical stresses already existent during cooling, causing the cracks to follow a vague pattern perpendicular to the principal stress direction. As a result, I'd guess that rock probably came from an area with mountain building or tectonically active at some point long ago in the past. 

[chickenminer]

I'd say it looks like a gneiss to me also, and have to agree on the 'slots'.

Don't think a piece of gneiss would be used to "sharpen" flint/chert arrowheads anyway.

Cool pattern on the rock anyway!

[Geologyhound]

Quote

6 hours ago, chickenminer said:

I'd say it looks like a gneiss to me also, and have to agree on the 'slots'.

Don't think a piece of gneiss would be used to "sharpen" flint/chert arrowheads anyway.

Cool pattern on the rock anyway!

I may be off topic here, but I travelled over Top of the World Highway once.  Aside from the beautiful sights, I always get a little smile when I remember how Chicken, Alaska was named.  Ptarmigan were plentiful but nobody could spell it.  So the residents named it Chicken instead.  😊

Beautiful sights up there - harsh winters, but beautiful sights.