What type of clay is the "blue clay" I have in my garden at home? Is it suitable for crucible making?

I've read up on some crucible material recipes, and they usually mention kaolinite and different types of clays. I've got plenty of high purity clay in my backyard, but I can't quite bridge the linguistic/geologic gap between my type of clay and these recipes.In swedish, the clay we have here is called blålera, or "blue clay". I've concluded this is also glacial mud or glacial clay. Googling that is hopeless though, because it's just wellness and spa type of stuff.Does anyone here know how I could figure out what actual type of clay it is I have, so I can apply that to the crucible recipes that exist? Is the blue clay I have suitable for making a ceramic crucible for instance? It's performed quite well in the green sand I made for casting. via /r/Metalfoundry http://ift.tt/2FTRug8