Not all Stainless is Induction...
This was just a quick test as I've been on a pot pan buying hunt and noticed on AC FAQ, they said to test if the copper core was induction *latest lineup*, then use a magnet.
I've always assumed all stainless is equal to a degree - and lo and behold, I guess the skin of my AC CC pan is not thick enough to hold the magnet I was testing
And not everything has to stick to a magnet to prove that it's induction ready. I bought a ceramic pot and it works on induction.
That is true. AC can be used on induction but the core does limit the efficiency. On the other hand, Chantal which is enameled inside and out and has a carbon steel and copper core is very efficient and fast. Swiss Diamond is producing pieces for an induction cooktop, Le Creuset is another option, the simple black steel pans from Matfer work well too. The magnet test is not always the most accurate test.
Basically the 18/10 stainless steel that is preferred from cookware (most stain resistant) does not work with induction. So most induction compatible SS pans have an extra layer, of a different steel, bonded to the base. Often the induction layer has a very flat bottom, and well defined edge, even though the inside of the pan is rounded. Obviously induction compatible pans can be constructed in other ways, but this is a common one.
I do have one induction compatible 'pan' that is not magnetic, or at least weakly so. It is a SS mixing bowl that is labeled 18/10. So the magnet test is not infallible. Especially if looking at new pans, it may be better to look for a 'induction' symbol on the pan label. Most European brands indicate stove compatiblies, either on a label or stamped on the base itself.