Rock ID Help Please

[Node]

Found In southern WI.  Weird one due to the difference between the outside and window cut. Looks like there is some volcanic crust on the outside but a lot of it looks to be weathered away.

Last Closeup pic of the outside is not color correct due to the lighting used.  
 

Any help with its ID is surely welcome.

 

[Hardtimehermit]

Looks like a volcanic rock, but maybe a limestone. Drop some acid on it hcl and if it  fizzes then it's limestone. 

[2Valen]

Looks like regular old limestone that I see all the time around here in central Illinois.

 

[Node]

7 hours ago, Hardtimehermit said:

Looks like a volcanic rock, but maybe a limestone. Drop some acid on it hcl and if it  fizzes then it's limestone. 

Thanks HHH.  What type? Nitric, Hydrochloric, Sulfuric?   At what concentration? 

[Node]

4 minutes ago, Node said:

Thanks HHH.  What type? Nitric, Hydrochloric, Sulfuric?   At what concentration? 

Too early.  Missed the HLC.  Dropped some 34% HLC onto the cut surface and no reaction was noted.

[Node]

6 hours ago, 2Valen said:

Looks like regular old limestone that I see all the time around here in central Illinois.

 

With a blue interior?   

[DDancer]

If you have not done so yet check out the sticky in this part of the forum on basics to identify rocks.  What I'm seeing looks like a metamorphic rock, likely a granite or fine grained pegmatite.  It looks like there's some feldspar in it.  As to the color differences that is due to weathering, again the video's by Chris can provide some good explanation as to why this occurs.  Pictures in natural light help as indoor lighting generally has a limited spectrum and true coloration are hard to get.

[Againstmywill]

Interior looks like basalt.

[Randy Lunn]

If you breathe on it and it smells "earthy" and "musty" than it is limestone. But it looks volcanic.

[Snoball Solar System]

That's a greywacke river cobble, but the interesting thing is the nodular brown rock scale, on 'one side only'.

I suggest that the nodular brown rock scale is comet spatter delivered to southern WI by way of an eject curtain composed of ice sheet fragments, from a primary (Clovis comet) impact on the Laurentide ice sheet, 12,800 years ago.  The rock scale is on the side of the river rock exposed to the secondary impact, which is why the scale is on one side only.

These same massive ice sheet fragments are suggested by others to be responsible for creating the Carolina bays along the Atlantic and Gulf coasts.