bill256
off to a rocking start
Member since May 2015
Posts: 2 
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Post by bill256 on May 20, 2015 15:35:28 GMT -5
My son and I went and found some rocks we thought were interesting. I was wondering if anyone could help identify what type of rocks these are and whether they're good for tumbling.   Thanks for your help. Bill |
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Post by johnjsgems on May 20, 2015 15:52:40 GMT -5
Look like chalcedony. Likely a lot of the exterior staining will tumble off so not very colorful. Tumbling rocks your kids found should be worthwhile. For the beginner, you can test rocks easily by scratching with a knife. If they scratch they will not tumble easily. If the knife leaves a metallic stripe that rubs off (metal transfer from the blade) they are hard enough to potentially tumble well. I collected beach rocks for many years on the Central Calif coast. Most would tumble well. There were always some trouble makers though.
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Post by 150FromFundy on May 20, 2015 17:09:54 GMT -5
Another good hardness test is to see if your rocks will scratch a piece of glass. Glass has a hardness of about 5.5. If the mineral will scratch glass it is harder than 5.5 and is a good candidate for tumbling based on hardness. Another good hardness test is to see if a steel file will scratch your rock. A steel file has a hardness of about 6.5. If a steel file will not scratch your rock, your rock is harder than 6.5 making it an even better candidate for tumbling. Here is a good link that will explain Mohs hardness scale, how to do scratch tests, and the hardness of common objects like glass, knife blades, and steel files. geology.com/minerals/mohs-hardness-scale.shtmlOnce you find hard rock, you then want to focus on fractures which can be a problem for tumbling. Good luck. Darryl. |
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bill256
off to a rocking start
Member since May 2015
Posts: 2
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Post by bill256 on May 21, 2015 11:16:11 GMT -5
Thanks for your help. I started them tumbling last night.
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Fossilman
Cave Dweller 
Member since January 2009
Posts: 20,723
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Post by Fossilman on May 21, 2015 15:44:46 GMT -5
Looks like a good haul and will polish great......
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SirRoxalot
freely admits to licking rocks
Member since October 2003
Posts: 790
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Post by SirRoxalot on May 24, 2015 9:28:17 GMT -5
The smaller, whiter pile looks like flint, and the other pile is quartz.
Both are great for tumbling and will polish beautifully.
Looks like you two have a natural eye for collecting tumbling rough, that's a nice start.
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