Need help on this one .. Looks like chert to me. Gentleman on local Facebook/yard sale is calling this ""Geode with Early Quartz Cluster"" need your opinion on this thanks...
Banded agate or banded jasper. Cherts tend to be black and white with sharp cleavages like flint, a relative of chert, and your specimen shows flaking more along the lines of agate and jasper. The reds lead me to believe its more jasper than agate but both are in the same family.
Geodes have open interiors of crystalline structures and banding around the central vug. Geodes can be considered hollow agates that just have not filled all the way in. Geodes are also stand alone stones. The piece you have looks to have come from a bigger matrix and the crystal pockets are vugs inside the host rock. Nice piece though.
I think it's called a nodule when it's filled in. A geode is hollow. Not positive but I think so. That is awsome !!!! I've been looking for a geode all summer and have not found one yet. I live in western pa. I have fun looking though .