Obsidian

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mohs
In Memoriam

RIP mohstly

Member since January 2009
Posts: 19,412

Obsidian Oct 22, 2012 15:18:58 GMT -5

Quote

Post by mohs on Oct 22, 2012 15:18:58 GMT -5

Hoping to have discussion on grinding/polishing obsidian,
Obsidian is probably one of the easiest mineral to grind;
yet, the most difficult to get scratch free
Those scratches, flat spots, imperfections, really show
due to obsidian glassy reflectivity

This is a piece that I sanded on belts up to 1200 grit.
Then I buffed on leather with C/O.
I think my sanding is pretty good.
Got a fairly even dome & pretty scratch free.
Although I haven’t looked at it under a loupe!!!

Anyway the C/O on leather buff polished it
but only achieved a matte sort of shine.
A bit disappointing.

This obsidian as greenish matrix of some sort in it.
Not great quality stuff? So I’m thinking the green stuff under-cut
contributing to less than stellar results.

Anyone know what that green material would be?
Any other suggestions about proper obsidian cabbing?

Thanks
Ed

dazagneiss

mohs
In Memoriam

RIP mohstly

Member since January 2009
Posts: 19,412

Obsidian Oct 22, 2012 22:34:59 GMT -5

Quote

Post by mohs on Oct 22, 2012 22:34:59 GMT -5

Welll this is vast improvement!
although the pictures sucks
taken inside

anyway I just went back to 600 grt
and ground it up to 15,000 grit on the Pixie

then I buffed it on a felt wheel
with 15,000 diamond paste
what a difference!

Thing is I don't know why the leather with C/O
didn't bring up decent polish?

I thought it was the green inclusion in the obsidian undercutting
I think that's a wrong theory

and I think the green inclusion is magnesium
fairly common in ob...

o well I'm pretty happy with the result
time to wrap it
and take a picture in the daytime

thanks for your help

Ed

dazagneiss

mohs In Memoriam RIP mohstly Member since January 2009 Posts: 19,412	Obsidian Oct 23, 2012 11:49:23 GMT -5 Quote Select Post Deselect Post Link to Post Member Give Gift Back to Top Post by mohs on Oct 23, 2012 11:49:23 GMT -5 Hi Guys ! This is the finished product I’m pretty happy with the polish/shine as noted it was buffed on hard felt wheel 15,000 diamond paste obsidian going to become a quest as the season progress stay tunE
	dazagneiss

metalsmith Cave Dweller Member since October 2012 Posts: 1,537	Obsidian Oct 25, 2012 14:52:12 GMT -5 Quote Select Post Deselect Post Link to Post Member Give Gift Back to Top Post by metalsmith on Oct 25, 2012 14:52:12 GMT -5 Re green colour - it could be that there is some chromium interacting with Aluminium oxide. Mg gives black, and tho' Fe could if reduced give green, this is unlikely. High Fe obsidians tend to be 'blood' obsidians... not green!
	It's not a typo ... it's English! You're only given one little spark of madness - you mustn't lose it - Robin Williams Sometimes it is the people no one can imagine anything of who do the things no one can imagine - Alan Turing

mohs
In Memoriam

RIP mohstly

Member since January 2009
Posts: 19,412

Obsidian Oct 25, 2012 15:26:25 GMT -5

Quote

Post by mohs on Oct 25, 2012 15:26:25 GMT -5

That's real interesting metalsmith
my experience with ob
is that much of it as greenish tint to it
especially when polished

chromium interacting with aluminum
cool
for some reason I though Mg might be that inclusion

the coloring metallic inclusions in rocks
really is an interesting study
i haven't found a layman type book on it, yet
thanks
ed

I hope to do another ob experiment real soon

dazagneiss

Woodyrock driving up their electric bill Smile! Member since January 2008 Posts: 2,719	Obsidian Oct 27, 2012 1:57:09 GMT -5 Quote Select Post Deselect Post Link to Post Member Give Gift Back to Top Post by Woodyrock on Oct 27, 2012 1:57:09 GMT -5 I think you started out with a junky piece of obsidian, and worked way too hard for that polish. Woody

mohs In Memoriam RIP mohstly Member since January 2009 Posts: 19,412	Obsidian Oct 27, 2012 7:31:36 GMT -5 Quote Select Post Deselect Post Link to Post Member Give Gift Back to Top Post by mohs on Oct 27, 2012 7:31:36 GMT -5 kind of the story of my life ;D mostly
	dazagneiss

mohs In Memoriam RIP mohstly Member since January 2009 Posts: 19,412	Obsidian Nov 3, 2012 19:19:22 GMT -5 Quote Select Post Deselect Post Link to Post Member Give Gift Back to Top Post by mohs on Nov 3, 2012 19:19:22 GMT -5 Kris (hand2mouthming) sent me a really pure slab of obsidian The slab broke in half in shipping but that's all right I'm a master at 2 pieces I've never possess such glassy lucent ob Really looking forward to cabbing Thanks Kris! Ed
	dazagneiss

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