V. cool fossil piece (cupstone- notcupstone)! The others will be impossible to id. Your lithic (as has been mentioned) cleaves in a way that make fragments appear/present as a point shape. I have the same trouble where I am. But you need to take a close look at signs of manufacture. NAs were not a crude people- and they made their tools with intent and care. In few instances, they used crappy material which didn't hold up well over time. Sometimes the chemical/mineral content of your local soil (for whatever reason) degrades your stone faster than under typical circumstances. Regardless, there's always, always more than 1 indicator proving you have an artifact, and 'shape' is only one.
The slimy/dissolving stuff is probably some stage of siltstone, but not 'stone' yet. Clay, sure/maybe, but not something worked or made by NAs. They fired their work, and it's a fairly durable thing- with preserved textures and patterns, shapes and so on. Washing fired NA pottery- even if using a soft brush- will not degrade the material. Also, drain pipes were glazed. But I have no idea what that glazed shard you have actually is. Sometimes there's simply no way of knowing for certain. If you want to take the deeep dive into pottery, glazes and the eras during which they were produced and the items those glazes typically were used on, that's your business. People have spent a lifetime's work studying pottery shards and glazes as well as how they were produced. So... good luck with that...
I admire your enthusiasm! Keep looking- and be sure to truly think about what you're finding. A triangle shape is not necessarily a point- even tho it's pointy. A cup in a rock is not necessarily a cupstone. Right now is a really good time to spend some time on line- on archaeological sites and not just Google image searches, so you become familiar with verified artifacts, lithic characteristics, etc. Good luck!
