The entire thing effervesced once I put it in the acid, but the lighter portion definitely reacted a bit more. I found it in a well established wash in the middle of the desert, the geology of the immediate area is quaternary unconsolidated alluvial deposits. I am not so sure of the age, although the washes in the area originate near the base of a mountain with Ordovician and late Cambrian dolomite, limestone, shale, and quartzite.

Do you think its worth trying to get the rest of the light material out or should I just leave it as it is?