pizzano
Cave Dweller
Member since February 2018
Posts: 1,390
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Post by pizzano on Nov 19, 2018 18:14:24 GMT -5
I just got around to cutting and "cabbing/slabbing", polishing via trim saw, Dremel and elbow grease this material..........:
It's the obvious black/grey and white layered stones we pulled out of a mine shaft entrance in Mercer City, Tooele County, Utah. It was part of a vein we followed and when we pulled on it (needed a bit of effort), it slid out in an elongated "tree branch" form....about 20" long. It broke in half as soon as we brushed it clean of mud.......:
Here's a poor pic of the polished side......: The striations in the dark part of the material are not grinding scars, they are actually embedded in two directions throughout the stone.
Here's another poor pic of the reverse side un-polished....:
Any ID help is appreciated......It's also my very first attempt at hand polishing a slab.....like always, I seem to inherently pick the worst stone types to try anything new.....was the same case with rotary and vibing on my first attempts....!
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metalsmith
Cave Dweller
Member since October 2012
Posts: 1,537
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Post by metalsmith on Nov 22, 2018 17:02:45 GMT -5
Black sediments could be any of: Mud, marl, pelagic ooze, black limestone Meta could be slate or marble Marble being metamorphosed limestone and not just a term for miscellaneous polished stone.
The critical test for marble / limestone is acid & check for bubbles. Nice friendly acids like ascetic (vinegar) or citric (lemon juice) should do the trick.
On dark rocks you’ll likely need magnification to check for bubbles (confirming carbonates) as the acid liberated CO2 due to the higher proportion of on carbonate matter. The darker = more non carbs.
Slates and schists require texture which appear to be absent here but correct me if I’m wrong...
HTH
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pizzano
Cave Dweller
Member since February 2018
Posts: 1,390
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Post by pizzano on Nov 22, 2018 18:06:18 GMT -5
Black sediments could be any of: Mud, marl, pelagic ooze, black limestone Meta could be slate or marble Marble being metamorphosed limestone and not just a term for miscellaneous polished stone. The critical test for marble / limestone is acid & check for bubbles. Nice friendly acids like ascetic (vinegar) or citric (lemon juice) should do the trick. On dark rocks you’ll likely need magnification to check for bubbles (confirming carbonates) as the acid liberated CO2 due to the higher proportion of on carbonate matter. The darker = more non carbs. Slates and schists require texture which appear to be absent here but correct me if I’m wrong... HTH Thank you for the clues....!
Early on during cleaning and cutting of the rough, I applied a 50% solution of hydrochloric (muriatic) acid to a few residual pieces. No visible signs of frothing or "bubbles" on either the white or dark portions of the stone........thinking slate or marble based material may react. Also tried 100% vinegar, arriving at the same results......no bubbles......basically eliminating limestone and marl aspects.
Any obvious texture being absent on the darker stone.......however, the white has an "opal" like silky smoothness......more so after polishing.
Appreciate the observation......I'll keep digging into this.....!
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Post by stephan on Nov 24, 2018 1:50:51 GMT -5
Perhaps something like graywacke (metamorphic sandstone), with the white being quartz. It's usually not quite that dark gray, but I've seen it.
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