p40whk
starting to shine!
Member since October 2018
Posts: 45
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Post by p40whk on Nov 6, 2018 9:12:08 GMT -5
I just bought a bunch of mixed rock for tumbling and went to separate it when I realized I don't know my rock well enough to figure out what is what. I did a search for a Mohs tester both here and on google and didn't really come up with anything here and google came up with a set of pics for $100 which I really don't want to spend. I saw this Diamond Tester on Amazon that looks like it has a harness scale on it but there aren't a lot of reviews to figure out if it would work for other stone and the only other testers I've found are Durometer testers which I don't think will work. Do any of you use a tester to figure the hardness of a rock you aren't sure about and if so, what do you use?
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Post by hummingbirdstones on Nov 6, 2018 9:31:13 GMT -5
Quartz is a 7 mohs, so if you have a quartz point laying around you can use that to see if the rocks you have are harder or softer than a 7.
Your fingernail is 2.5. If you can scratch a stone with your fingernail, it's softer than that and will probably disappear in the tumbler.
A penny is a 3.
A steel knife blade is about 5.5.
Between these you should be able to at least get close.
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p40whk
starting to shine!
Member since October 2018
Posts: 45
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Post by p40whk on Nov 6, 2018 9:42:11 GMT -5
Than's, that's a lot easier than spending $100!
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Post by rmf on Nov 6, 2018 9:47:19 GMT -5
hummingbirdstones is correct for the hardness of a penny as long as the penny is pre 1982. In 1982 they changed the composition of the penny from 95% Cu amd 5% Zn to 99.2% Zn and 0.8% Cu with a plating of pure copper bringing the total to 97.5% Zn and 2.5% Cu so I am not sure how this changed the Mohs hardness of the penny. It may be insignificant just keep in mind there is a difference.
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p40whk
starting to shine!
Member since October 2018
Posts: 45
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Post by p40whk on Nov 6, 2018 9:50:56 GMT -5
hummingbirdstones is correct for the hardness of a penny as long as the penny is pre 1982. In 1982 they changed the composition of the penny from 95% Cu amd 5% Zn to 99.2% Zn and 0.8% Cu with a plating of pure copper bringing the total to 97.5% Zn and 2.5% Cu so I am not sure how this changed the Mohs hardness of the penny. It may be insignificant just keep in mind there is a difference. I'll have to go through my jar of pennies now!
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Post by rmf on Nov 6, 2018 9:54:29 GMT -5
FYI some 1982 pennies are the original alloy some are the new. You can tell the diff by the weight. 3.11 grams for the original and 2.5 grams for the new.
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Post by hummingbirdstones on Nov 6, 2018 10:04:21 GMT -5
Good catch! Didn't think about the change in the formula of pennies.
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NRG
fully equipped rock polisher
Member since February 2018
Posts: 1,630
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Post by NRG on Nov 7, 2018 22:03:44 GMT -5
The only important tester is a pocket knife. If a knife does not scratch it, lump it together. My
The only exception is glass and obsidian. A knife won't scratch them and they won't tumble will with harder stuff.
Anything softer than a knife will scratch and won't tumble well.
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