Stone(Jade?) Buffalo carving

I found this guy in a thrift store and he immediately grabbed my attention. My first thought was marble or granite but after finding a few things online I'm not so sure it's not grey/black Jade. The first thing I noticed about it was how heavy it is. Secondly that red spot on it immediately made me think it had rust on it which made no sense at the time but after some reading I learned that what is called black or grey Jade gets it's darker color from a high iron content in the Jade. To me this could explain the spot that looks like rust and the green hue that appears on it makes me wonder if it isn't in fact Jade. Of course I would rather it be Jade than marble but if anyone has any insight as to the origin of this beautiful piece I would more than love to hear it.