Is onyx a black and white banded agate or a black chalcedony?

Question

Which one is the more correct description

Answer 1

They are all microcrystalline (actually cryptocrystalline) quartz as you seem to already know.  I think agates are a type of chalcedony.  Onyx can vary in color as well so I would say it could be a banded or black chalcedony given your choices but I have never heard it referred to as such.

Answer 2

Onyx is the name given to chalcedony which is uniform in color, generally black or white.

Onyx is a chalcedony quartz that is mined in Brazil, India, California and Uruguay. It has a fine texture and black color;

I have never seen white onyx.  It is nearly always black, but not banded anyway, and it is chalcedony, not agate.  So, the second answer is correct:  black chalcedony

Answer 3

agate is a completely different type of semi-precious stone. also, onyx is generally jet black, so it would have to be a black chalcedony