Need Help ID Black Rock

Oklahoma Digger

Jr. Member
May 14, 2013
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Found this rock on a top overpass bridge above an interstate freeway (a lil risky but I got it lol). Any ideas? Basalt in Oklahoma? Weight is 299 grams. A bit heavy for its size and attracts a magnet. Looks busted up a bit. Been seeing this rock for awhile driving to & from work. A bit curious what it is. I see some rust spots as well. Thanks in advance!
 

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bmartin0693

Sr. Member
Feb 22, 2012
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East Bend, North Carolina
Primary Interest:
All Treasure Hunting
Depending on the size of the crystals, are they visible under a magnifying glass? If crystals are coarse grained then it could be a intrusive rock called gabbro that formed below the crust. Basalt is fine grained and extrusive, being formed above the crust. Looks like yours has vesicles (cavities) also. I think its basalt from the picture provided. You found this on an overpass really? It could have fell out of the back of a dump truck b/c basalt does have uses in construction and groundwork.
 

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Oklahoma Digger

Oklahoma Digger

Jr. Member
May 14, 2013
78
17
Depending on the size of the crystals, are they visible under a magnifying glass? If crystals are coarse grained then it could be a intrusive rock called gabbro that formed below the crust. Basalt is fine grained and extrusive, being formed above the crust. Looks like yours has vesicles (cavities) also. I think its basalt from the picture provided. You found this on an overpass really? It could have fell out of the back of a dump truck b/c basalt does have uses in construction and groundwork.

Yes, I can a bunch of them under mag glass. Thx bmartin...
 

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