What is it?

[Tizzy]

Hi All-
No better way to spend your time waiting for triple A, by looking fir rocks!!
Found this while waiting for a tow truck by the railroad tracks here in East Texas.
Pretty neat white and black combo. But, what is it?
Please, help identify?!

Thank you much

 

[ToddsPoint]

If it was found here up north I'd say it's an igneous rock, likely porphyry. However, not sure the stuff occurs in ETX. Maybe it fell off a train from up north! Gary