To do a quick on-site test roll the damp clay into a snake coil and then wrap it up like a pretzel. If it allows you to do this without cracking or falling apart then it deserves saving for further testing. I also make a small pinch bowl just so I can play with it and see if it will hold a shape. I leave these two pieces out in the sun to dry and then throw them into my next kiln fire at whatever temperature I am firing at the time. When I get them out of the kiln I thoroughly examine them and even break off pieces as I check the color, texture, shape, etc... This quick little test will tell you a lot about your new found clay.