testing more rocks

Wave Man

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@Aussie123; was good enough to send me some samples of some rock for me to spark test and compare them to flint as I did with in my quartz vs flint comparison, here are my results.

what was sent



I really like the chalcedony it is IMO very close to flint and on par with the best petrified wood for sparking ability.
 

Chigger

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It's surprising what minerals will produce a good spark. At various campsites some river stones, chert ? and another camp granite started my fire.
 

Wave Man

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chert is just another name for flint mate, but don't try and ask me to define it and be able to tell you the difference between chert and flint. I have had geologists try to explain it and all I did was come away more puzzled.

Apparently it is about usage.....I thought it was about colour and what layer the flint was found but apparently I was somewhat wrong.

I have seen the term chert and flint being used interchangeable. I honestly think even experts really don't know the difference.
 

Wave Man

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I really like that chalcedony, it sparked as good as flint and wasn't chippy or fragile. It was a very interesting stone, easily as good as flint or the best petrified wood I have used.

It developed the sharp edges we look for with flint and steel and seemed to be quite robust.
 

Aussie123

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Hi Wave Man, thanks for the great review.

I dug up a few photos showing where the rocks came from.

But first here's a close up of the quartzite. I had these on the table and notices the way the light was hitting.
You can clearly see the conchoidal fracture.
These type of fracture occur in fine grained materials which don't have any internal structure.
This is the same type of fracture you see in glass, flint and many of the materials we favour to knap

The bit I circled is the point where I hit the rock to flake off the chip; and you can see the lines radiating out from that point.
Understanding and making use of conchoidal fracture is key to good knapping, and quite handy when looking for a rock to use with a steel ...
20200827_111608.jpg 20200827_111729.jpg 20200827_111608 - Copy.jpg

This rock came from the Lake Eyre basin area on a large, deflated clay pan:
P4281924.JPG P4291927.JPG


P4291928.JPG

I think this is the other half of the flake I sent to Wave Man … There was tones of quartzite, but to need to stop and have a look, you can't tell much from the car:
P4291932.JPG


Chalcedony is a type of chert (flint, agate, opal, petrified wood, and many other "gems" etc are also types of chert).
Cherts are formed as "micro"-crystalline sedimentary deposits. There are lots of varieties of chert, but its probably best to think of them in terms of their "gem";
we all sort of know what an opal is, or petrified wood etc

Driving through sand dunes we suddenly drove over a "gravely patch" …. I had to stop and check it out, rocks don't appear on top of a sand dune,
so I know this was something worth looking at:

P4201092.JPG P4201110.JPG

Some big bits too:
P4201112.JPG
 

Wave Man

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thanks Aussie for the expansion, great pics. I forgot to ask where you got the samples from and buggered it up on the video, I need to learn to do more background before shooting.

I was really surprised by the Chalcedony, but learning that it is a type of chert explains a lot.

As I am learning we do have viable rock for 'flint' and steel, it just might not be in the form of flint.
 

Chigger

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From what I can glean chert is a mineral that has been compressed and heated to make it very hard. There are many different sorts of chert and is a different sort of mineral to flint.
 

Wave Man

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well here it is

https://www.gemsociety.org/article/what-is-the-difference-between-chert-flint-and-mozarkite/

form that article
Flint Is A Variety of Chert
Although there is a lot of confusion on this, chert refers to cryptocrystalline or polycrystalline quartz that usually forms as nodules in limestone. Flint is reserved for such material that forms in chalk or marl. Flint is simply a type of chert. (At least this was the distinction that was made in the literature when I was a geology student 35+ years ago).

The Moh's hardness scale.
1 is talc
2 is selenite,
3 is finger nail or calcite
4 is Fluorite
5-5.5 is steel
6 is jade
7 is chert, quartz, tiger eye, jasper. All silicon dioxide stoves even petrified wood.
8 is aquamarine, emerald, and other beryls
9 corundum like rubies and sapphire
10 diamond.

if they weren't so expensive I'd love to spark test some of the 8's, 9's and diamond's (10) but as shown it's all about the sharp edge so you have to shatter the rock/crystal to form those sharp edges so you can drive sparks off it and I don't think many of the higher hardness stones (above 7) shatter like that.

Plus you don't necessarily need a hardness of 7 stone to drive sparks as I have seen one bloke use obsidian (5.5 Moh's) and get sparks on steel.
 

Aussie123

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….

8 is aquamarine, emerald, and other beryls
9 corundum like rubies and sapphire
10 diamond.

if they weren't so expensive I'd love to spark test some of the 8's, 9's and diamond's (10) but as shown it's all about the sharp edge so you have to shatter the rock/crystal to form those sharp edges so you can drive sparks off it and I don't think many of the higher hardness stones (above 7) shatter like that.

Plus you don't necessarily need a hardness of 7 stone to drive sparks as I have seen one bloke use obsidian (5.5 Moh's) and get sparks on steel.
I do have a pile of beryl and some low grade garnet .... if I find them, I'll let you know …
 

Aussie123

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I was a bit surprised by the porcelain. It should have a hardness of approx. 7, but will vary a bit.

When I tested it I thought I consistently got some OK sparks, not great, but OK ….

But that's the great thing about side by side testing.

Great tests Wave Man, thanks again
 

Wave Man

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not a problem Aussie I love doing this sort of thing. Thank you for giving me the opportunity to do it mate. I hope it is interesting to the forum.

The porcelain did spark somewhat but I had to work very hard to get it to go, and I nearly failed with it. The main problem was the edge, the platform wasn't right and it was hard to lay the char cloth right at edge so the sparks fell into it properly.

I love to test some beryl and some low grade garnet, as I said never fooled around with any rocks with that high hardness.

I am going to have to get my hands on a largish piece of obsidian as well, apparently it can be done and I am determined to do it. RockyInstincts sells it so I'll get a piece off them.
 

Boogers

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I found the motherload this weekend, big white rock about the size of a baseball that sparks good. I'm guessing it's quartz, but when I google it there's so many different types.

I'll have to look at making it smaller without exploding it. It's good to know we can find stuff that works, maybe not as good as flint but at least we have options.
 

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Aussie123

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I found the motherload this weekend, big white rock about the size of a baseball that sparks good. I'm guessing it's quartz, but when I google it there's so many different types.

I'll have to look at making it smaller without exploding it. It's good to know we can find stuff that works, maybe not as good as flint but at least we have options.
With quartz you should expect to have quite a lot of collateral damage when you start to flake it.
Its just how it shatters. Hopefully you'll get a few nice pieces out of it (but expect a fair bit of debris too)
 
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