181lizard
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Post by 181lizard on Aug 17, 2006 13:04:19 GMT -5
I dug this hunk out of a dirt pile a couple of blocks from my house. Not totally sure what to call it. I'm thinking it's just a piece of jasper. Two different colors in it...red & yellow. (or golden color) What do you think? bBy the way...just what is chert?
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wades
starting to spend too much on rocks
Gottfried Reiche (1667-1734)
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Post by wades on Aug 18, 2006 8:18:03 GMT -5
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rollingstone
starting to spend too much on rocks
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Post by rollingstone on Aug 24, 2006 3:55:58 GMT -5
I'd call that jasper -- nice reds in that piece.
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Sabre52
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Post by Sabre52 on Aug 24, 2006 10:02:36 GMT -5
Lizard: Usually books separate jasper and chert only by origin. Both are more or less non transluscent microcrystalline quartz. Chert and flint are said to be from sedimentary sources where the silica usually originates from overlaying diatomaceous layers oceanic in origin and true jasper originates from sources where the silica comes from volcanic sources ( ash etc) as the overlaying deposit. Chert and flint therefore are often associated with limestone rocks while jasper is usually associated with rhyolite, andesite or basalt. Lots of confusion here in the west as we have situations where both origins are present in the same area and often the terms are used interchangably anyway *S*..mel
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Post by deb193 on Aug 24, 2006 10:31:22 GMT -5
Thanks Mel ... I have been wondering about this distinction myself.
Any idea why flint and some cherts are usually preferred by knappers?
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Sabre52
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Post by Sabre52 on Aug 24, 2006 10:37:37 GMT -5
Daniel: Since the flints and cherts are more prone to come from areas that are more non seismic, my guess would be they are less prone towards internal defects that would cause the knapped pieces to break at unwanted times. Since jasper is from volcanic areas which seem to be more geologically active, I guess it might more often be flawed. However, here in California, even the cherts are flawed because of all the dern earrthquake activity....mel
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181lizard
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Post by 181lizard on Aug 24, 2006 11:35:04 GMT -5
So if I read this correctly...there's really not much difference between the two? But given the location this was picked up at...probably could call it jasper?
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181lizard
Cave Dweller
Still lurking :)
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Post by 181lizard on Aug 24, 2006 11:36:55 GMT -5
Not that I really care WHAT it's called! (It's still cool to find something out of my ordinary!) But if I ever talk to someone about rocks...I prefer to have a smidgen of knowledge rather than be a dolt!
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Sabre52
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Post by Sabre52 on Aug 24, 2006 13:28:31 GMT -5
lizard: No drastic physical difference between jasper, chert, flint etc. All microcrystalline quartz and the same chemically. Actually chert used to be the rockhound slang term used for any low quality jasper without much fancy color or pattern and that's where some of the confusion comes from. I'd think you'd be pretty safe calling that specimen jasper though due to the location.....mel
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