This specimen was found along a creek in Washington state.  Most of the jade in Washington is nephrite and comes in a variety of colors ranging from green to grey.  Jade is difficult to find and identify.  If you see a green rock lying on the ground it is not jade.  Jade almost always has a coating (rind) caused by oxidation.  Jade can be identified by the whitish/tan coating (seen in the photos below), its heft (jade is heavy), the high pitched ping made when hitting it with a hammer and by the milky solution that forms when you rub it with water.  This piece captures both the inner polished beauty of jade along with the rough, deceptive coating that hides this beauty from the unknowing eye.

Rock type: Jade (most likely nephrite)

Nephrite is a metamorphic rock that forms from the metamorphic transformation of serpentines in lower pressure and temperature conditions.  It is an amphibole mineral.

Chemical composition: Ca2(Mg, Fe)5Si8O22(OH)2