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ID this rock with a wierd (melt?)structure
  
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Kara




Joined: 22 Jul 2018
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PostPosted: Jul 22, 2018 19:46    Post subject: ID this rock with a wierd (melt?)structure  

Please help me to identify this rock from Finland. There seems to be some kind of a melt structure (?) on both sides I have never seen before.

Could this be an impactite of some kind, or something else? What do you think? The pictures are taken wet and dry, hence the big colour variation.

Thank You very very much for your help! (and sorry for my bad English).
- Kara, Finland



2b-001.JPG
 Mineral: don't know
 Dimensions: 7*4*5 cm
 Description:
 Viewed:  382 Time(s)

2b-001.JPG



2-001.JPG
 Mineral: don't know
 Dimensions: 7*4*5 cm
 Description:
wet
 Viewed:  383 Time(s)

2-001.JPG



1b-001.JPG
 Mineral: don't know
 Dimensions: 7*4*5 cm
 Description:
wet
 Viewed:  384 Time(s)

1b-001.JPG



3-001.JPG
 Mineral: don't know
 Dimensions: 7*4*5 cm
 Description:
wet
 Viewed:  385 Time(s)

3-001.JPG



1.JPG
 Mineral: don't know
 Dimensions: 7*4*5 cm
 Description:
 Viewed:  384 Time(s)

1.JPG



3b.JPG
 Mineral: don't know
 Dimensions: 7*4*5 cm
 Description:
 Viewed:  361 Time(s)

3b.JPG


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Justin Hickok




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PostPosted: Jul 22, 2018 23:57    Post subject: Re: ID this rock with a wierd (melt?)structure  

Looks like conglomerate to me but don't take my word for it.
I leave that to the pro's.
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Pete Modreski
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PostPosted: Jul 23, 2018 07:51    Post subject: Re: ID this rock with a wierd (melt?) structure  

Kara, I'm pretty certain that this is an igneous rock you have. It's a fairly fine-grained porphyry; magma that cooled, not real fast as in lava on the surface, but not very slowly deep underground that forms coarse-grained granite. The white grains are feldspar (orthoclase) crystals that formed in the cooling magma. Rock like this usually forms in dikes, where the magma was intruded not too far below the surface, so it cooled an a "moderate" rate. It is probably what we call an "intermediate" composition igneous rock--not granite or rhyolite, not basalt, perhaps a dacite in composiition. And the glossy/glassy patch, is probably a patch of silica (quartz or agate) that formed in an open space in the rock.

Pete
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James
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PostPosted: Jul 23, 2018 09:38    Post subject: Re: ID this rock with a wierd (melt?)structure  

I agree with Pete. Reminds me of similar igneous rocks from Scotland
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Kara




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PostPosted: Jul 23, 2018 11:48    Post subject: Re: ID this rock with a wierd (melt?)structure  

Thank You Justin, Pete and James! And thank you Pete for the informative and detailed answer you gave me. Perfect forum for me to learn! - Kara
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