Monday, June 7, 2010

Newfoundland Chert Photos

Chert outcrop on the Port au Port Peninsula
Here's a few more photos of chert for those folks interested in such things.  Chert is the kind of stone used by the aboriginal inhabitants of Newfoundland and Labrador to make their sharp stone tools, like knives, scrapers, and arrowheads.  I collect it to make reproductions of those artifacts.

Port au Port Peninsula

 The Port au Port outcrop is made up of a six metre thick bed of chert nodules that range in size from as big as your fist to the size of beach balls.  The nodules remind me of marshmallows floating in hot chocolate.  The forth between the marshmallow nodules is very crumbly and fractured, but the individual nodules themselves can be solid.

The Port au Port chert bed reminds me of marshmallows in hot chocolate

The little sucker marks on this core are actually impact marks from tide-tossed rocks.  There will be little remnant hertzian cones just below the surface under each of those little scars.

The four images below are all fresh flake scars from Port au Port chert - you can see a bit of buff coloured mud in one or two of the photos, but for the most part they are clean surfaces.  If you enlarge the photos you'll see what looks like white or silver dust on the surface.   Those little random constellations are actually the pyrite crystals that lace the material. I think they are especially clear in the second and fourth photo in the series.





Gravel Quarry north of Botwood

In contrast with the Port au Port outcrop which contains a remarkably uniform grey chert with pyrite inclusions, the gravel quarry north of Botwood contains a lot of variety.  You won't seen any chert as fine grained as the Port au Port material in the photos below, but keep in mind that they all come from a single location about the size of a hockey rink.


"GRAD PART"is spray painted on the back wall of the quarry


Sometimes you can get lucky with solid, fine grained chert with nice patterns. The orange at the top is the cortex.

Sometimes is grades into a flat red or brown.

Nice colours, but this stuff tends to have a lot of internal fractures.

Still workable, but a much coarser chert with gritty inclusions.
This is the same stuff as above, but without the big inclusions - on the surface its a good look-a-like for a core of Ramah Chert.  However, the light grey is not translucent and its much tougher to work than Ramah.

Some subtle banding.

Not bad - but quite coarse.

This bright green material is rare in the quarry, but its nice to find small pieces of it.

The best, most common material is this green-grey chert.  It doesn't have a lot of internal warping or fractures.


This purple, green and buff banded material forms a vein that cuts across the whole quarry, but its tough to work and prone to internal fractures.  Too bad, I think its the prettiest rock there.

A fairly reliable piece of grey chert, but you can see some surprise fractures in the upper left hand corner.

This is similar to the Port au Port material, but you won't find any pyrites here.

This variety isn't too bad to work and it has nice speckles and patterns in it.

I'm not sure exactly what created the speckles - sometimes they are vesicles (holes) like this one, but in other pieces they are inclusions.

Grey and black banded chert.

This was the first piece I saw when I opened the car door. I was actually still sitting in the drivers seat when I took this photo.  It might be natural, but I also suspect that it may have been inadvertently heat treated by the bonfires in the quarry because I've never found an in situ band of this colour or quality of chert.
 Photo Credits: Tim Rast

3 comments:

  1. This makes me want to get out rock collecting. I don't know if there are any good (or any) chert sources in NS, but we have some gorgeous agates and amethysts and some really cool fossils.

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  2. The potential for colour change through heat treating is a nice side effect of altering the rock's flaking properties. Have you done much, or do you plan to do any future experimentation with heat treating your newly collected lithic materials?

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  3. The Botwood material seems like a good candidate for heat treating. The Port au Port material doesn't need it and the only experiments that I've done with heat treating local material was with Port au Port chert. It ruined the rock. I got the impression from those experiments that Newfoundland chert didn't require heat treating - which I still mostly believe. But just because some of it doesn't require heat treating doesn't mean that other sources couldn't be improved by heating. The Botwood material is tough enough that is may be worth the effort to start experimenting with heat again. And as you say - it could open up some cool new colour and texture options.

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