ID help (MI serpentine?)

stdenis_jd

Hero Member
May 7, 2015
513
576
West Lower Peninsula, MI
Primary Interest:
Prospecting
Curious to see some opinions on this one. Found it in a gravel pit in North central lower peninsula of Michigan. It's the green one, can post pics of a slab if it is helpful. My first thought was a form of serpentine, but I don't have any first hand experience ID'ing it sinc 20170611_140141.jpge I've never seen anything like it around here (gotta love dem glaciers!)

Grainy texture
Somewhat conchoidal fracturing, leaning toward his an uneven fracture pattern.
Hardness is about 6.
Fairly heavy/dense, solid build (no natural pitting or irregularities).
Opaque, no translucency.
It's looking like it will take a fantastic shine too, love the black stripes in it :-)

P.S. the black ones are mahogany obsidian, pink is Kona dolomite, red & white are Michigan puddingstone (jasper & white quartz sand conglomerate), and green/blue is chrysocolla)
 

Post pics of the rough. Slabs don't do us much good, can't see the luster.
To hard for serpentine.

If you'd said it was translucent I'd gone with: Epidote, Diopside or Aegerine.

Opaque, well...? Turquoise? But it seems unlikely to have outlived glacial transport, but hey, what do I know?
 

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The luster might be altered from the mineral oil from my slab saw. Dried it off pretty good tho.

Retested the hardness and it's definitely 5.5-6.0 max. 5.0 won't scratch it
 

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I'm thinking Hornfels or another kind of rock. Not a mineral, really.
 

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