Can any geologybros help me identify this rock? I'm only

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Thread images: 3

Anonymous
2016-01-04 16:32:10 Post No. 7761799
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Anonymous 2016-01-04 16:32:10 Post No. 7761799 [Report]

Can any geologybros help me identify this rock? I'm only a first year so I don't know shit.
It has well-defined layers that go all the way through and it's partially coated in what I think is bitumen (or whatever it is they stick roads together with) and I found it on the way into a field that had been surfaced with broken chunks of tarmac. There were other similar rocks nearby.
I gave it a few whacks with my hammer and the rock didn't break and sparked once. The fracture looks vaguely conchoidal but without the arcs you'd see on flint. Couple more pics through my hand lens to come

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Anonymous 2016-01-04 16:34:16 Post No.7761805
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Anonymous 2016-01-04 16:34:16 Post No.7761805 [Report]

Is it hard?

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Anonymous 2016-01-04 16:36:33 Post No.7761808
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Anonymous 2016-01-04 16:36:33 Post No.7761808 [Report]

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Pic of a fractured surface (scale is millimeters)

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Anonymous 2016-01-04 16:37:58 Post No.7761811
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Anonymous 2016-01-04 16:37:58 Post No.7761811 [Report]

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1 MB, 2448x3264

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Anonymous 2016-01-04 16:39:18 Post No.7761814
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Anonymous 2016-01-04 16:39:18 Post No.7761814 [Report]

>>7761805
not scratched by steel, just looking for something harder

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Anonymous 2016-01-04 16:40:18 Post No.7761817
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Anonymous 2016-01-04 16:40:18 Post No.7761817 [Report]

>>7761814
Then it's definitely a rock.

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Anonymous 2016-01-04 16:43:43 Post No.7761821
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Anonymous 2016-01-04 16:43:43 Post No.7761821 [Report]

>>7761805
>>7761814
tungsten carbide from a pull-through sharpener doesn't scratch it either

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Anonymous 2016-01-04 17:05:25 Post No.7761847
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Anonymous 2016-01-04 17:05:25 Post No.7761847 [Report]

>>7761808
>>7761808

By the way fractured surface looks i would say comon micritic limestone. But its nearly impossible to know without knowledge of regional geology where the sample came from :(

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Anonymous 2016-01-04 17:21:13 Post No.7761868
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Anonymous 2016-01-04 17:21:13 Post No.7761868 [Report]

Its some sort of rock alright

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Anonymous 2016-01-04 18:54:31 Post No.7762033
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Anonymous 2016-01-04 18:54:31 Post No.7762033 [Report]

>>7761847
Either what this anon says, or if no HCL reaction test for hardness. If it's around 7-8 I would say quartzite. Honestly I think quartzite is more likely than the limestone. pics 1 and 3 look like quartzite and 2 more like the limestone at least to me.

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Anonymous 2016-01-04 22:28:29 Post No.7762416
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Anonymous 2016-01-04 22:28:29 Post No.7762416 [Report]

>>7762033
Seconding quartzite on the basis of surface texture pic three. My second guess would be onyx on the basis of banding and conchoidal fracture.

If you're dying to know, you could test its hardness on a window pane or pick up some muriatic acid from a hardware store to test for carbonate minerals.

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Anonymous 2016-01-04 22:43:38 Post No.7762450
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Anonymous 2016-01-04 22:43:38 Post No.7762450 [Report]

>>7761821

it's diamonds