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Author Topic: Dacite or Obsidian?  (Read 6038 times)

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Offline ionicmuffin

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Dacite or Obsidian?
« on: May 30, 2013, 01:11:11 pm »
Got some big rock here, not sure if it's obsidian or if it's dacite. It was given to me by a friend from their property.
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Amo innectis arcus- I love crafting bows (latin)

Offline TRACY

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Re: Dacite or Obsidian?
« Reply #1 on: May 30, 2013, 01:34:52 pm »
Send it to me and I'll let you know what it is >:D

Looks like black obsidian, but I'm not the expert on obsidian favors like Sparrow or Bubby are. I'm sure someone else will step up and give you more accurate info.


Tracy
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Offline Will H

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Re: Dacite or Obsidian?
« Reply #2 on: May 30, 2013, 02:03:23 pm »
Obsidian
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Offline ionicmuffin

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Re: Dacite or Obsidian?
« Reply #3 on: May 30, 2013, 02:05:36 pm »
sweet! if i can make this darned thing stay together in once piece i may be able to procure a decent biface! of course after i get to that stage well have to see how that goes...
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Offline Trapper Rob

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Re: Dacite or Obsidian?
« Reply #4 on: May 30, 2013, 10:33:13 pm »
 Looks like obsidian should make a nice blade.
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Offline JackCrafty

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Re: Dacite or Obsidian?
« Reply #5 on: May 30, 2013, 11:04:22 pm »
Yep, obsidian.
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Offline ionicmuffin

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Re: Dacite or Obsidian?
« Reply #6 on: May 31, 2013, 02:55:30 am »
sadly its not going to make a nice blade... i tried to get some kind of flaking going, it just crumbled at every hit... it must have been above ground during a freeze
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Offline aaron

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Re: Dacite or Obsidian?
« Reply #7 on: May 31, 2013, 11:59:30 am »
as far as I know, dacite is actually a form of obsidian- we just call it dacite to differentiate it, but it is chemically rhyolite, like all obsidian. knappable dacite comes in two varieties I know of regular opaque grey and "black butter". here's a pic showing the regular, the butter is glassier and darker. Neither have much banding or color variation.
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Offline YosemiteBen

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Re: Dacite or Obsidian?
« Reply #8 on: June 01, 2013, 12:35:11 pm »
Obsidian and Dacite are indeed technically the "same" thing. Dacite has less silica and is heavier in other minerals, hence the lack of glassiness.  If you spend enough time with the stuff like any other material then you will be able to see the differences.  Typically the only time obsidian will not yield some type of flake is if it has a lot of pumice in it.  The little pumice pockets do not allow for good flake formation.  Other wise you may not have and angle less than 90 degrees, are hitting it too straight, not high enough on your perceived platform or hitting it hard enough. 
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Offline ionicmuffin

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Re: Dacite or Obsidian?
« Reply #9 on: June 01, 2013, 12:40:20 pm »
i did see pockets of something, tons of the stuff too, i thought it was crystals but i guess it could have been pumice too.
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Offline Sparrow

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Re: Dacite or Obsidian?
« Reply #10 on: June 02, 2013, 02:05:13 pm »
Surface stone can be fractury,but also, it depends on how the flake was struck sometimes,stuff that has been struck from a boulder or ledge with a steel hammer or sledge will have stress fractures thru it.you can see them on the stone. Big copper mauls and large hammerstones seem to fracture the rock alot less.  '  Frank
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