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...................that is awesome Zeke. I rather think that looks like a fossil cast of a sponge, or a crinoid head. I know you might think me eccentric for saying that, but I have found so many types of fossil evidence, and many soft tissue creatures were able in the most exceptional situations capable of being replicated over time with minerals as they permineralized. There are several bits of common evidence I think I see in your photos, that are most probably predatory worm holes(flatworms) then filled in with accessory minerals from the local environment of that time. I suspect a Crinoid head more then a Sponge, because the high amount of iron minerals(hematite red)present that replace blood. I also think I would call this an Agate without seeing and touching it up close. Does that look like a quartz vein cutting through it also? The black looks like a patina of Siderite or Goethite or Magnetite I think. A very awesome looking little rock. Please don't be too astounded at the idea and possibility of it being a fossil cast. I have found that the highest percentage of fossils to be deformed and of quality to poor for museum display, often looking nothing like what they are the fossilized remains of..................

................conferring with my copy of the Audubon field guide of north american fossils, I seriously consider that looking like a Crinoid head just somewhat deformed. The cavity on the one side looking like the opening of the crinoid throat, somewhat flattened and deformed as it was buried under sediments, and successfully fossilized because of and aneroibic envoironment......
...............if you don't want it send it to me............

You have some bold ideas. I think that vien through the black is the same stuff as the bulk of the rock. The black is what gives me pause...your list of possibilities is also apt, those are the contenders i had in mind. the geology isn't right for fossils, though we know that just a generalization. Of course we were prospecting for jade. we thought we were just hitting a documented area...just looking for a good acess point...but ended up finding a totally different creek with it's own source load....so this came from a jade bearing creek, near source...not too likely to have much glacial deposits either as the creek is down to bed rock mostly....saw no glacial till signs either. the black suspects are also found in evidence in,on or around jade.

oh, and the black can't be scratched by a knife if that narrows it down

Very interesting looking. It does almost look like a fossil in it.